I cannot give editing permissions to my colaborators

I'm having trouble with giving permissions to my colaborators to edit my sheet. I give the permissions with the top-right button in the sheet (no trouble with that), but when my colaborators log-in with their personal accounts to edit the sheet, they find only visualization permissions. I've tried everything, from changing them to delete some of my colaborators and giving the permissions again, with no success. Do you know what could be happening?

I have now a Pro license (with supposedly 10 colaborators, now none of them can edit the sheet). originally, this sheet has been built in trial period.

Thank you all!!