Let me start off by saying that I don't know if this will fix the issue for everyone!
I built a new gaming machine over the holidays, as well as reinstalled EQ, MQ, and Innerspace on a gaming laptop I had lying around.
After completing both, neither would allow me to use any IMGUI windows. Including CWTN plugins, MQsettings, and ButtonMaster to name a few. If I loaded the toons from MQ and not from InnerSpace, I could get those windows to work. This did get a little frustrating trying to troubleshoot, but I was able to get myself a workaround.
Let me also say that before building the new Desktop and redoing my Gaming Laptop, I was able to get this working on the latest versions of all applications involved, and now it's not working.
I was able to ultimately get everything working again by rolling back Innerspace to an older version.
The sweet spot for me was version 1.19, version 7242
If you are having similar issues, you can install the latest version of Innerspace and, from a command prompt (I ran it as Administrator), run the following command.
"%programdata%\Lavish Software\utils\lavishbuild" install innerspace live "1.19 Build 7242"
This will rollback the Innerspace version to the one I was able to get working on both my desktop and laptop.
Also, a note here: Even after getting it working on this version, if I updated to any version newer than this one, it would start with the issues again.
If someone comes up with a permanent solution to update to the latest version of Innerspace, I would be happy to try it out, too.
Hope this helps someone else out.