Spellcheck (F7) not working on Studio 2021

Hi, All of a sudden my spellchecker has stopped working. I finished a translation (package received from a client) and wanted to run a spellcheck. But neither pressing the "Check Spelling" soft key nor F7 does open the pop-up window which usually performs the spell check. I have not changed any settings on my computer and hitherto the spellchecked worked fine.Verify (F8) is working fine, as is everything else.

Studio 2021 SR1, version 16.1.3.4096, Windows 10.

Any suggestions what to do?

Thanks a lot.