Symptoms
When trying to copy an item to M365, ShareGate Migrate displays the following message:
There was an error while trying to add the "Application_Name" application at the destination.
Error code
ST-275-171
Details
This error occurs when ShareGate Migrate tries to copy to an element that requires a specific application to a SharePoint online site. ShareGate Migrate will automatically try to add this application to your destination site and it will display this error if it fails to do so.
Solution
The easiest solution is to add the app manually on your destination site and retry your migration:
In your browser, navigate to your destination site, then click on the gear icon at the top-right of the page.
Click on Site contents.
Click on "add an app".