Nope. The authentication/perms issue would have been reported with the error code 5. The only other thing left to try before doing an In-Place upgrade of Win7 (which will certainly resolve the issue) since you don't like Win10 is to try and get a ProcMon capture of the whole Process:
Step#1 - Capture Process Monitor Trace
1. Download and run
Process Monitor. Leave this running while you perform the next steps.
2.
Try opening the CP just like you have in the past.
3.
Stop Process Monitor
as soon as it throws the error. You can simply do this by clicking the
magnifying glass on the toolbar as shown below.
4. Select the
File menu...
Save... and save the file to your
desktop. This is likely the default location. The name (unless changed) will be
LogFile.PML. This is fine.
5. Zip up and provide the link to the
LogFile.PML file. Examples of services to upload to are
Dropbox or
OneDrive or
SendSpace.