There are 3 possible solutions for this issue :
1. Install FSRealistic in a different location than your Program Files. It works best if you install it on a different drive than your boot drive (your OS drive). A restart of the computer might be necessary.
If you already have profiles defined, make sure to copy your Profiles folder from the original location into the new one.
2. If you have installed FSRealistic in your Program Files, you will need to run MSFS as admin in order for it to be able to run FSR automatically. To do that, right-click MSFS executable, and choose Run as administrator
3. Make sure FSRealistic is not blocked by your firewall or antivirus software.
Thanks, rkApps.
FSR stopped working. I dont know why. The only thing I did was install GSX pro. I dont know how that could corrupt it, but everything was working before.