Text won't paste in Numbers

I'm using Numbers 10.1 on a MacBook Pro (Mid 2012). My Os is Catalina 10.15.7. Suddenly I'm finding that when I copy text from a Pages document, then try to paste it into a cell in Numbers, it won't paste. I've tried using both the File/Paste menu and the keyboard Cmd/v, but neither works.

Only if I go to the Format pallet, then select Cell, and re-select the Data Format as Text, then it pastes, but having to do that is taking so long that I'm finding it quicker to re-type the words into each cell because the text won't paste. This is a real bind because I'm trying to create a rather big spreadsheet right now and it's going to take me hours and hours.

Is there some setting I'm missing? Although I don't recall changing anything lately.