MySQL ODBC stopped working overnight

You guys will love this.

This company has an in-house project management system. It's the core of their business, and they are lost without it. They are aware it needs to be migrated to something more modern, but after 5 years, that project still hasn't started.

I was asked to look into a network issue, but this isn't network but SSL I think. Let's first show the architecture:

- The server is a CentOS 7 running MySQL Community Edition 5.7.16 - Clients connect from Windows 11 with a 32-bit MS Access, using a 32-bit MySQL ODBC driver v5.3.13

Since yesterday, they get a "protocol version mismatch". The server wasn't accessed since 18 October 2016 (haha), so I presumed a Windows update might have disabled some SSL version. But: I see no relevant Windows update, and if I manually allow every possible SSL version and encryption algorithm, it still doesn't work. What *does* work however, is downgrading the ODBC driver from version 5.3.13 (from 2019) to version 5.1.13 (from 2013), further adding to my confusion.

The cherry on top: the single guy responsible for this application is on a one year sabbatical.

Edit: Found it, but leaving this here for anyone stumbling on the same issue. The MySQL_Server_5.7.15_Auto_Generated_CA_Certificate had expired after 10 years