Criteria for hiding tab error is too broad
There is an error message in place to prevent hiding every tab that displays this message:
"The workbook must contain at least one visible worksheet.
To hide, delete, or duplicate the selected sheet(s), you must first insert a new sheet or unhide a sheet that is already hidden."
This error also comes up when there is only one tab open and you select unhide.
The only way around this is to open a new tab to unhide the other tabs. I would suggest reviewing the criteria for this error message so that it is not triggered with unhide.