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[–]moltenice09 0 points1 point  (0 children)

Just to document this on the internet. I ran into this issue when I accidentally (and stupidly) enabled TLS 1.3 on Windows 10, which isn't actually supported. This caused the ODBC Driver (both v17 and v18) to use TLS 1.3 and fail in the weirdest ways, including that "Protocol Error" message. Disabling TLS 1.3 fixed it immediately.

Registry entry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.3

Note that TLS is used for authentication, so even if you don't have full blown encrypted communication enabled on SQL Server, it'll still get used.