JRiver Media Center 18 Suddenly Won't Play New MKV ver 1.12.3 Blu-Ray Rips

[DMark1]

Title says it all. Older stored mkv bluray rips are playing fine on JRiver Media Center 18, but not new bluray rips made using current makemkv version 1.12.3. (1.12.2 didn't work either) New rips won't start playing at all, just shows a black screen. I can jump around in the movie using jriver's controls and it will display one frame only. Fast forward and reverse works and displays frames in fast forward or reverse, but regular Play won't work. I am running Windows 7 Pro on a dedicated machine.

How do I fix this? Is Makemkv 1.12.3 no longer compatible with JRiver MC18? I am not an IT guy or programmer, so please keep responses simple with step by step instructions if possible.

[Woodstock]

If you rip a movie that is currently working using 1.12.2 or 3, does that also not play?

I'm wondering if it's a case of a video codec that JRiver doesn't understand. Some older players can't handle VC1 Interlaced, for example.

[DMark1]

I am having the same issue with JRiver 18. Will upgrading to the latest version (Jriver 26) solve this issue?