Hi! I have an Arduino nano. I programmed it in arduino-ide_2.2.1_Windows_64 bit is your firmware, but the SPD-Reader-Writer-20230930 program does not see it. What's wrong?

Firmware 20231207 is not compatible with older versions of SPD-RW. Download https://github.com/1a2m3/SPD-Reader-Writer/releases/tag/20231210 

Hello! I flashed and launched the latest SPD-RW. The same thing.
Maybe I assembled the diagram incorrectly? Although this should not affect the definition of Arduino in the program.
P.S. The arduino is serviceable!

That is possible, even bare Arduino won't get detected, it will get stuck at resetPins() line in the setup() procedure. To bypass that, replace resetPins() with resetPinsInternal() on line 167 and reflash the Arduino. If it is detected after that, check your circuit again.

After replacing line 167, the device was detected. It means something is wrong with the scheme. Thanks for the help!

Hello! I checked the whole scheme. When resetPins() is on line 167, the SPD-RW program, the arduino is not visible. When reset Pins Internal() is on line 167, it sees but does not start and outputs the log:
[Info] 13.02.2024 18:55:29: Program started (v. 2.23.12.10, Core: 2.23.12.10 ) (Included FW: 20231207)
[Info] 13.02.2024 18:55:39: COM5: Initializing device (115200)
[Info] 13.02.2024 18:55:39: COM5: Connecting to device
[Info] 13.02.2024 18:55:41: COM5: Checking firmware version
[Info] 13.02.2024 18:55:41: COM5: Checking name
[Info] 13.02.2024 18:55:41: COM5: Checking I2C clock
[Info] 13.02.2024 18:55:41: COM5: Checking RSWP
[Info] 13.02.2024 18:55:42: COM5: RSWP unavailable
[Info] 13.02.2024 18:55:42: COM5: DDR5 RSWP disabled; Offline mode unavailable
[Info] 13.02.2024 18:55:42: COM5: DDR4 RSWP disabled; High voltage control unavailable
[Info] 13.02.2024 18:55:42: COM5: DDR3-SDRAM RSWP disabled; High voltage and SA1 controls unavailable
[Info] 13.02.2024 18:55:42: COM5 connected (Name: User, FW: v.20231207)
[Info] 13.02.2024 18:55:42: COM5: Ready!
 
Can you advise me what to do next?

I need a bit more info on your setup. Do you have any RAM connected, what type? The log shows you can connect, but RSWP is disabled, because it either doesn't see any RAM or high voltage feedback isn't set up properly. If you used different config pins that the ones suggested, you'll need to edit SpdReaderWriterSettings.h file before flashing.
 
After connecting, show your device info. Click Device > Info.

4GB DDR4 test memory. I do everything according to your scheme. I use arduino nano on ATmega328P.  Maybe for your circuit, you need Atmega168P? This is my first time working with Arduino. The output HV_EN at the time of initialization is 2.3 v, at the 1st leg of the optocoupler is 1.8 V. The resistance is 330 ohms. The optocoupler does not turn on. accordingly, on HV_FB - 0. Optocoupler PC817.

Your voltages are way off. At idle HV_EN should be near 0V, the optocoupler's collector (pin 4) should be near 9V, and its emitter (pin 3) should be at 0V. Even when HV_EN is high, it should be either near 5V, or 3.3V, depending on model used.
 
Have you tried another optocoupler or a different Arduino board? (Either ATmega328P or Atmega168P based boards are fine.)
 
Remove the optocoupler first, and check the voltage at the HV_EN pin first. If voltages are still abnormal, you might need to replace your Arduino board.
 
Then apply 5V output to the optocoupler's current limiting resistor (R3) and check the voltage at its emitter. If it is still at 0V, the optocoupler doesn't turn on and needs to be replaced.