@blades808 Just WOW!!!
That is amazing work.. I wish I had the patience to do that

@larsbrubaker sorry I could "play" earlier
YAY!!! At a first look all is well again! Thank you for your hard work!!

@larsbrubaker Wonderful
Thanks for being on the case too BTW!!!

@larsbrubaker there is no need to do a gif, the visual is this..
Right click on the object - the Right click menu appears
left click on the "export" and the menu just disappears.. and nothing happens.

It is like the "export" menu that SHOULD appear simply does not exist in the code. - all the other menus pop up from the right click menu fine..
If you click on the "drop arrow" on the save button and then "export" then again, nothing . nada... It just disappears like the next menu doesn't exist .
I don't know what the common thing is that makes this not work, but I have done a CLEAN install on this PC and it doesn't fix it - If it was linux I would say it was likely a permission issue
with the menu... but it isn't

(EDIT) I can't see links to old versions on the page you said
(and the links on that page don't work LOL)
(edit) I found them here http://wiki.mattercontrol.com/Release_Notes

@larsbrubaker Hi again.
so.. The old version you posted does not export, the hotfix does not export...

1. I uninstalled & removed all the user data and installed the OLD one you posted, and no export.
2. updated that and no export.
3. found the really old (2019) install file on my old PC ( which is now running a WORKING 2.20.11.10679 ) but the install I found was 2.19.1.10116 - and installed it and export WORKS...
4. updated it using teh "update" in the program and is STOPPED working.

Note I deleted user data between each full install - so it is NOT the user data as I though. The last working version i know of then is 2.20.11.10679 which I cannot re-install as the OLD one you supplied ( 2.21.4.10901) seems to have the same problem as the current one, so I think you need to go back a few more versions to find a working one (IMHO)
This was all done in a rush

@larsbrubaker Re-installing the old version is not working either .. I will do another test, after uninstalling the current one

EDIT _ Ok uninstalling the current one & installing the old one didn't work..
All my "workspaces" were still there ,. so the error is prob NOT in the exe, but in the user data somehow,, I am busy with work now, but I will find & NUKE all my user data when I can and see if the OLD version allows exports again.. I am in a rush right now, so will try a bit later

@larsbrubaker Thanks, but still not working for me either.. made no difference at all

I had to fire up an old PC that had an old version installed yesterday, then tried saving the work I had done and could not export as an .MCX file and tried to open it in the old version. but it didn't work and I had nothing ...
So I had to start from scratch in the OLD version , on the old PC, and do the whole object again .. so I could export it as an STL.
Keep working on it please

@larsbrubaker Personally, I would take the stable update off your server post-haste before too many more Win10 people fall in this hole as the week starts in Europe!

@larsbrubaker As others stated, there is no error , nothing.. I am on Windoze10 64bit.
Nothing will export, new stuff, old stuff, so I doubt it is the file itself.

I just update to the latest stable release and no I can export either!!
This is a disaster for a Monday morning
Using Windows 10 64bit -
All that happens when clicking on export is that the menu disappears, no error nothing ..