I renewed my Office 365 Personal subscription last week. Each time I open a saved Word document I get the error message in the subject title. I never received this message in last year's subscription. It only happens since my renewal.
I have tried:
1) Settings>Apps>Default Apps>Choose default apps by file type for each of the various doc files, templates etc and made Word the default app
2) Repair Wizard and run the Online repair
The version of Microsoft Word for Office 365 32-bit. The version of Windows 10 Home version 1809 and it is 64-bit. Could this be the cause of the error?