Jenkins slave cannot connect with master: Incorrect acknowledgement sequence

Question

After update of our Jenkins master installation to its latest LTS version 2.46.3 one of its slaves (Windows 7 machine, 32-bit) cannot connect with the master.

The er

Answer 1

This happened to us when a Windows Update or some other silent background update messed with the slave's environment variables. HTTPS_PROXY and HTTP_PROXY had to be re-added, and once that was done we were back in business.