This is due to Play Integrity. Google deliberately makes custom OSes unable to pass this, so GOS cannot become certified. There is nothing you can do about this at the moment. This is not an issue with GOS or one GOS can fix, but an issue with Googles monopoly and entirely their fault.
Play Integrity is being marketed as a security feature while absolutely not being one in the slightest bit. It only permits devices with stock OS that license GMS and bundle the prilveged Google Play Services. It also allows those even if they are EOL and without updates for 10 years. If it really would be about security, it would require regular updates, supported devices and obviously would permit GOS.
Play Integrity is merely a tool for Googles monopoly.