Hello, Try this so you don't lose your work.... Export>>IDMLClosed down Indesign, reopen, see if missing functionalities are reinstated (if this doesn't work try and reboot your entire computer).open the IDML and save as to INDD. Regards,Mike
Sorry to hear about this. Would you mind sharing the version of the OS & InDesign? Does it happen with a specific file or all? Are you able to export? If yes, please follow suggestion given by @mikeb41294032 & let us know how it goes.
This information will help us assist you accordingly.