Microsoft licence on my Mac has disappeared and now I can't access my files

Since updating when I tried to open my Microsoft Word and Excel files they asked me to purchase Microsoft 365 licence. I had purchased the Microsoft Office HS 2019 and had been using it on nearly daily basis since. I spoke to Microsoft who have managed to direct me delete something so I cannot even access my files. When I try to sign in it says I have two accounts and other times it says there is no account linked in.

Microsoft say it is an Apple issue.

Any help with this would be appreciated