Looks like Sony pulled the 5.5 version installer from their site. The Softronic site was downloading the installer from Sony. Hopefully someone will still have a copy of the actual MSI file.
"RemotePlayInstaller_5.5.0.08250_Win32.msi"
That is the actual installer, but I can't find it anywhere. Just a few references to it.
See if you set a "restore point" on Windows prior to installing the update. You may be able to roll it back.
Your other options are Chiaki for remote play or the CronusMax Zen now fully supports the PS5.