I have never used it , the only thing that i can suggest you that if you can recall what changes that you made to any of the software from the last time that it worked.
I haven't made any changes, that's why its so puzzling.....Jerry
I do have the latest versions LR 5.7.1 & Photomatix Pro 5.1. Ibelieve that I started having the problem after I updated to Photomatix Pro 5.1. I uninstalled it from my computer programs files. I had a computer screen issue, it kept going black every so often. Was on the phone with Dell & they may have done something that changed some settings so I was advised by Photomatix Support Team to re-install the program, they gave me a link. I totally lost a program (CyberLink Power Director 10) due to Dell, I had to re-install it.
As you can see by the screen shots I have a problem.....Jerry
did you try to reinstall Photomatix? Before you reinstall rename the folder %appdata%\Adobe\Lightroom\Modules\Photomatix.lrplugin.
Its working fine now, had to go into the program & reset something per the
Photomatix support team. Thanks for the follow-up.....Jerry