Why gives invalid value when trying to enter something in this cell?

[secarica]

I have a cell where any attempt to enter a value gives “Invalid value”. I can clear the direct formatting and so it returns back to normal, but I am curious what format gives that behaviour (or where to look at, except to clear all formatting) ?

The cell was part of a bigger spreadsheet, but I reduced it to just one cell in a hope to be able to understand better the problem.

(the orange cell at A1 in the attached file)

locked_cell.ods (9.9 KB)

[mikekaganski]

It’s Data → Validity.

(What a nice question! Has an attached sample, not a useless screenshot; the sample is minimized; the position at which to look at is mentioned explicitly. If only all the questions were like this! )