Technique is everything - keeping the cooler parallel to the GPU Die is essential, while tightening in an "X" pattern, working each screw down a little at a time.
If the Gap is too large:
copper shims could be used if the gap was too large. Though your not supposed to need them, when installing this water block
WARNING: Too much pressure on GPU die will damage the die
Your photo does not really show what that gap is with the lighting & focus
"dry test - NO Power to card" Test with TIM & No thermal pads ... do you have good contact with GPU die ?
TIM is NOT for filling large gaps - it is meant to fill small imperfections in the surface
Are all of the standoffs tight, if you have the equipment are they all the same length ?
Good TIM spread
EK had an issue with some Asus GPU
Did you know? – Compatibility issues with Strix RTX 2080 Ti water blocks Very interesting Root Cause ... No idea if this could be the type of issue you are having ? I do not have the Hydro Copper
(excerpt & photo)
"A tiny layer of glue is present around the GPU die which interferes with the four closest stand-offs on the water block."