The fix for this issue is now available in the latest update of InDesign – that is, InDesign 15.0.3.
Please update your InDesign application to get the fix.
Adobe InDesign team
An error occurred while saving the commentAnonymous commented
Adding my voice here, spell check does not work for me either. Serious issue and needs to be fixed. Please push out an update,: this is a benefit of cloud software, to be agile and push updates, and it's not happening for this REALLY BIG GLITCH.