[galaxy-user] Problem Joining Two Datasets

Good Afternoon, I have been having problems with my Galaxy account. The upload issue I was having has been fixed, but now I can't seem to join two datasets. I have checked both text files that I want to join to ensure they have common columns, but there are no options available when I try the drop-down menu to select a sheet to join. I also get an error message stating "Either you are not allowed to view this history or the owner of this history has not made it accessible" when I first try to view one of my other saved histories, but then the files eventually appear for that saved history. Thanks, Kim