Excel Template won't work from MS Teams New Menu. Works from SharePoint New Menu.

[LizzyT]

In MS Teams, Click on New Menu and select uploaded Excel template from list. Then get this message.

Click Open in Desktop App and get this message.

This works in SharePoint.

I've done the same with Word templates and they work fine within MS Teams.

Just can't get the Excel Template to work in MS Teams.

Any ideas would be great?