RM/Cobol 12.07 and Win 10

Version 12.07 certainly precedes Windows 10.  So, my guess, is, yes, this is a compatibility issue.

Every new major version of Windows creates a whole new set of Windows compatibility issues.

The LOC 520 error indicates a problem with use counting.  The problem is specifically a mismatch between the use count value stored in shared memory and the value created by the runtime that has been started.  This probably only happens when two different versions with the same license are running at the same time.  By any chance do you have different versions of RM/COBOL on your system?  A later version of RM/COBOL such as 12.12 that is Windows 10 aware might calculate a different use count than an 12.07 RM/COBOL.  If you do have different versions that don't have different licenses (different serial numbers), then make sure you are not running the different versions at the same time.  It's also possible that a 12.07 use count service is not compatible with a 12.12 or later use count service (Liant RMUC Service).  This might mean that you need to restart your machine and only run one or the other version, never both.  You might also need to make sure that there are not two different Liant RMUC Service services are running on you machine, which might happen because installation of the two different versions of RM/COBOL installed different version of the use count service.