when I try to display values in a line diagram, I now only get the list of values; same for scatter plots.

It had worked with the same Excel program and the same Excel sheet, but suddenly the observed behavior showed up.

Also the frame around the selected values is red instead of black:

The data in the sheet comes from a CSV import, but that also had worked before.

Version info:

Microsoft® Excel® for Microsoft 365 MSO (Version 2403 Build 16.0.17425.20176) 64-bit

Questions:

• is there an explanation for the observed behavior, i.e. why is the selected data marked with a red frame instead of a black one?
• is it a bug or a feature and how can I return to “normal”?