The issue has been fixed in the latest release of InDesign – InDesign 2021.
Please update to this new version of InDesign to get the fix.
Adobe InDesign team
An error occurred while saving the commentJonas L. commented
***WORKAROUND*** (no software restart or computer reboot required):
This solves the issue of default shortcuts, such as CMD+N for New Document, not working.
1) Go to Edit > Keyboard Shortcuts
2) In the Keyboard Shortcuts menu, select a different "Set" than the one you want to use. I have a custom Set called "all_mine", so I simply select the [Default] Set instead.
3) Change the Set back to the one you want to use, in my case "all_mine" (no need to save or do anything else), and press the OK button.
This works for me in InDesign and Photoshop 2020 on a Mac. Your mileage may vary.
Best of luck, and please get this fixed, Adobe.