The remote server returned an error: (401) Unauthorized when importing a form template
When you attempt to import a form template you receive the following error.
It appears that this issue can occur if your tenant was created after August 2020 and it’s quite easy to resolve by running a single PowerShell command. You simply connect to SPO using the SharePoint Online Management Shell and then run the command. It can take a few minutes to take effect, in our case it took less than 5 minutes.
Connect-SPOService -Url https://yourtenant-admin.sharepoint.com Set-SPOTenant -DisableCustomAppAuthentication $false