Ran into the same situation with a 32-bit install on 64-bit Win10. The redistributable version does not seem to be the issue.
Tried registering the sonitus DLLs manually (in powershell running as administrator):
C:\Program Files (x86)\Cakewalk\Shared Plugins> C:\Windows\SysWOW64\regsvr32.exe .\SonitusFXCompressor.dll
And got this: