Hi,
I had a similar Problem on a couple of Computers.
On some it was fixed with the latest Version 12.1 RU1 MP1 (12.1.1101.401).
But I still had a computer where I could not install it. I opened up a support case and the helped me with the following solution:
To resolve this problem, adjust the value of the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\ registry subkey.
1. Click Start , click Run , type regedit , and then click OK .
2. Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\
3. In the right pane, right-click MaxNumFilters, and then click Modify.
4. Change the value to “14”, and click to select the Decimal option, and then click OK.
Note: Default value is 8, 14 is the maximum
5. Close the Registry Editor.
Then I uninstalled SEP => restart => install SEP => restart and now everything works fine