I am experiencing the same problem. I have tried uninstalling and reinstalling the software. I actually uninstalled 4.1 when the 5.0 version failed to run after installation. Now I am unable to run the previous RAS versions.
We are having the same issue now with 5.07 and with previous versions. We have got around it previously by just upgrading to the next version if available. But now that we are on the latest version we had to try something else. The reboot of Windows made no difference.
We are a Windows 10 professional site with re-directed personal folders (roaming profiles), so we tried running HEC-RAS 5.07 as a local administrator whilst still logged in as the regular user. This worked and HEC-RAS ran. Closed the software and ran the software as the regular user, and it worked also. Maybe that has fixed the issue for this user. Time will tell.