Cannot create new or copy a sheet in Excel

I have a workbook with 5 sheets, which is not very big, and I cannot copy or create new sheets. The error that comes up is "This action won't work on multiple selections".

I checked that there are no multiple selections of cells or sheets as well as all other things suggested in this thread (apart from workaround through Excel Online, do not have one):

https://answers.microsoft.com/en-us/msoffice/forum/msoffice_excel-mso_mac-mso_mac2016/this-action-wont-work-on-multiple-selections/33bdfd4d-c59d-4061-af02-78786b1d37eb

Any ideas what else can be done?