Version 9 Premium

I have a paid version of TeamViewer 9.  It has the last update for that version.  I have this version on all of my clients PC's that I remote into.  Some of my clients would like to remote from home to do work on occasion.  In the past I have been able to distribute my Host version to these clients and it worked without issue.  Now, when a client tries to connect from home, they get a Version Mismatch error.  Even if they upgrade to 14 to try to connect to their work PC (version 9), it gives the same error.

Is this working as intended now?  If so, how does a person use the free version?