A connection was successfully established with the server, but then an error occurred during the pre

cl27274 

Sorry, but that's out of my competence. What I'd that's first check in Data->Data source settings if they are correct for that source.

However, perhaps that's not Power Query issue. I googled a bit and first what found

A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.) (Microsoft SQL Server, Error: 10054) · Issue #563 · microsoft/mssql-docker · GitHub

Errors when applications try to connect to SQL Server in Windows - Windows Server | Microsoft Docs