Cannot suggest anyone to repair it but I’ve had a similar problem with a fwb 150 rifle and in the end I took it out of the stock, mounted it in a vice with the open cocking arm strapped back securely and removed the trigger block. Then gently eased the cocking arm for forward and allowed the piston to return to its uncocked
Position.
You can’t remove the entire trigger block on a 90 but I think you can release the sear manually.
Could try a similar thing, making sure the cocking arm is held back very firmly.
The electronic trigger on the 90 can be dry fired, and can be ‘clicked’ when it’s not cocked. It's a good way to check the trigger is working before you actually load it.
If you can de-cock it safely then check all the wiring is connected, and see if you can get it to ‘click’ which would indicate it would release the sear if cocked.
Sometimes the light doesn’t work but the trigger still clicks.
Good luck,
Matt