Since I upgraded to 2023, I've been having issues with the Material List under Machine Group Setup. Sometimes I go to select a material and the "mill-current" library will be blank even though I've made multiple custom materials. Re-opening the file can fix it but not always. Every time I select a material though and start programming, it clears the material when I go to post. If I go and reset the material, then edit a toolpath, and re-check the material, it's a 50/50 chance that it cleared it again. It just won't save the selection unless I set it and then post. If I close and reopen immediatley after saving and posting it clears it again. Any ideas? I can't find any solutions yet.

Thank you guys! KB5027215 is the culprit for my system but I am unable to uninstall the update. I tried from the update history page (uninstall option is not available for that update) and from the command prompt (says the update is critical and cannot be uninstalled). Thank you for posting the link to the myMastercam error page. I wound up having to change my code editor to CIMCO to get it to work again. I can get Code Editor to run now by opening a blank document first but I lost all of its functionality; no colors, multiple buttons at the top missing, can't remove block numbers anymore, etc... Guess I'm using CIMCO for now.

I'm having the same issue as well. Do you know which specific Windows update it is? Hoping an un-install of the update will fix the issue.