Hi, so I was folding away with a 1070ti, stepped up to a 2070 and I get this error message : Failed to start core: OpenCL device matching slot 1 not found, try setting 'opencl-index' manually  
 
I tried removing slots and resetting to default, I tried setting opencl-index to 0, also tried rolling back drivers to what I was folding successfully before on. 
 
Anyone have any ideas?

My suggestion would be to completely uninstall the drivers from Windows and reboot so it tries a default configuration and then install the latest drivers after the reboot.
 
Are you using both cards in the system now?

I've had this issue  twice with 10 series cards and the easiest fix to try worked for me both times. Put the 1070 back in, open fah and then remove the slot. Reboot with new card and add the slot.
I have not tried a 20 series yet and so I think what drougnor and rj mention above is nec as well.
 
much easier than searching through files
 
 

After you update or fix the NVIDIA Drivers.
Exit the Client Software
Deleted the file GPUs.txt from the \ProgramData\FAHClient Folder.
Start the Client backup.
You can also delete what is Bold Below.
And then add the GPU Back.
 
config.xml
<config>
  <!-- Folding Slot Configuration -->
  <client-type v='advanced'/>
  <!-- HTTP Server -->
  <allow v='192.168.1.2-192.168.1.253'/>
   <!-- Network -->
  <proxy v=':8080'/>
   <!-- Remote Command Server -->
  <password v='*********'/>
   <!-- Slot Control -->
  <power v='full'/>
   <!-- User Information -->
  <passkey v='*********************************'/>
  <team v='********'/>
 <user v='********'/>
   <!-- Folding Slots -->
  <slot id='0' type='GPU'>
    <paused v='true'/>
  </slot>
  <slot id='1' type='GPU'>
    <paused v='true'/>
  </slot>
</config>
 

I just wanted to pop in with my experience - I had to reboot several times after adding the 2070 to my system to get all three video cards to install cleanly. I ended up uninstalling all the drivers and added each card in order, starting with the 2070 the 1070 ftw and 1070 sc last. 
 
Once I got the drivers properly installed and seeing all three cards, I was able to fold with no issues other than having to remove the existing slots, saving, then adding them one at a time, adjusting all three values to match so each slot is indexed (0,0,0; 1,1,1; 2,2,2) uniquely.  Since I'm using the latest client, it picked up the newest video card list and got straight to work.
 
Now, on my motherboard, as soon as you put a vid card in all three of the PCIE slots, the bios won't display on the main output. I've since found there's a PCI/PEG setting I need to toggle to get that to display properly with all the slots populated, but so far, I have only to wait a little while for the OS to start loading the VGA drivers, then things display correctly.  This may be something else to keep in mind for other folders.
 
With ALL of the above in mind, if Koshogi is still having issues, esp with bluescreens, make sure that your PSU is powerful enough to support the extra wattage, that the PSU cables are solid and there are no faults in the line (Undervolting/wattage can cause issues when the card tries to go to full power) and if that all checks clean, verify visually there are no bits of debris causing unexpected shorts and, if you have the ability, test the card in another system. 
 
I hope you're able to get folding at full capacity and enjoy the new card, because it's worth the initial PITA to get going, in my opinion!
 
d

Yesterday I installed RTX2060 in my test rig and all I had to do was to update drivers to the latest version from nvidia website ( 417.71 ). It runs fine since yesterday. I was pretty surprised about the performance as it shows 1m ppd / gpu@ 2GHz.

Hi guys! sorry for the late response - I've been having a bit of a nightmare with the card. I managed to get it to fold in the end, by doing a clean driver install with DDU - I'm RMA'ing the card though because I'm getting random crashes in two games that I play.  
 
Thanks again for all the help!

Glad you got it to fold Kogoshi, unfortunate about the RMA. It happens from time to time. Replacement should be painless, EVGA's RMA service is really good. 

List all the Hardware that you are installing the RTX Card in.
Did you update the Bios on your Motherboard?
Is the Power Supply Less that 5 Years Old?
What is the Part Number of your 2070?
Are you using One PCIe Power Cable or Two?
Did you remove the Old Drivers and Run DDU in Safe Mode before you changed Cards?
After you installed the New Card did you Re-Set the Bios on the Motherboard?

bcavnaugh
List all the Hardware that you are installing the RTX Card in.
Did you update the Bios on your Motherboard?
Is the Power Supply Less that 5 Years Old?
What is the Part Number of your 2070?
Are you using One PCIe Power Cable or Two?
Did you remove the Old Drivers and Run DDU in Safe Mode before you changed Cards?
After you installed the New Card did you Re-Set the Bios on the Motherboard?

Ok so I have a brand new PC that I originally installed my 1070 ti in. Which worked flawlessly.  
 
i5 9600k
2x8gb corsair vengeance 3000 
rtx2070 Black - 08G-P4-2071-KR  (two separate power cables)
EVGA 750 G1+ supernova PSU
Temperatures never exceed 70c on anything under load. 
Currently on latest nvidia drivers, I've tried the past 3 versions
I use DDU in safe mode to clean install every time - including only installing drive + physx (I've actually done a hell of a lot of trouble shooting, including trying debug mode - nothing working)
I've tried increasing TDR delay, just makes the crash take longer to happen (PC hangs for several seconds instead of "render device lost" appearing instantly. 
Sometimes I blue screen with "Kernal mode overflow" or something, can't remember the exact error message.
Windows 10 Enterprise x64
 
I haven't been folding much recently, the crashes are happening when I'm gaming, in Overwatch and Monster Hunter World. I understand this is the folding forum so I wasn't asking for tech support or anything, just thought I'd update my situation - I'm grateful for you guys responding.  
 
 

It could be your CPU & RAM settings.

I'm using RTX Project 2080Ti

Win 10 Pro, Version 1803, Build 17134.407 on my X99 chipset
 
Nvidia 416.16
 
X1 0.2.9.0 (old version & hard to setup -- but its been running good for me)

Folding Client 7.5.1  (lots of false Errors to ignore)
 

Kogoshi
My CPU is overclocked, got it done by scan.co.uk, I had no problems with my 1070 ti - would be annoying and strange that a 2070 couldnt handle an overclocked cpu though?

After I changed out my GTX 1080 Ti Cards to RTX 2080 Ti Card and had to redo all my Bios Settings and set new OC Setting on the Motherboard as well as Updating the Bios on the Motherboard.
Others may tell you here on the Forum that you do not need to make any changes or update the Bios on the Motherboard.
But that is 1 out 10 users, the other 9 users had to update the Bios and Reset the OC on their Motherboards to use the new RTX Graphics Card.

What are your Crash Code?
I do not recall but did you uninstall the Folding Client Software and reinstall it after Deleting the Old Folders?
"EVGA 750 G1+ supernova PSU" Do you have a Bigger PSU maybe an 850 or 1000 to test with?
Are you still using 2 PCie Power Cables?

So you are Folding OK now