Can't seem to be able to write on datasheet

It seems like my app cannot write anymore on the datasheet
it was working yesterday, but is not anymore
any clues? some sheet rights that would have unexpectedly changed?

Are you over the 500 row limit? If not, do you have available empty rows in your desired sheet? If so, have you checked to make sure the rows aren’t being added to the very bottom (row 1000) of your sheet?