SSH not working after macOS 10.15.6 update

I am experiencing a timeout connection error when using ssh from my MacBook to connect to an external server. The problem started immediately after having updated to macOS 10.15.6. I could connect smoothly before that. The server is working correctly, I can connect from other machines.

$ ssh -v T800                   
OpenSSH_8.1p1, LibreSSL 2.7.3
debug1: Reading configuration data /Users/XYZ/.ssh/config
debug1: /Users/XYZ/.ssh/config line 22: Applying options for T800
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 47: Applying options for *
debug1: Connecting to xxx.xxx.xxx.xxx [xxx.xxx.xxx.xxx] port 22.
debug1: connect to address xxx.xxx.xxx.xxx port 22: Operation timed out
ssh: connect to host xxx.xxx.xxx.xxx port 22: Operation timed out

/etc/ssh/ssh_config contains a bunch of commented lines and then:

Host *
        SendEnv LANG LC_*

While /Users/XYZ/.ssh/config for T800 is:

Host T800
        Hostname xxx.xxx.xxx.xxx
        User john
        Port 22
        UserKnownHostsFile ~/.ssh/know_hosts

The firewall of my MacBook is turned off, and the one on the server is correctly configured. I can ping the server from my MacBook and I can access it via ssh from other machines, including my second MacBook wich is still running an older version of macOS.

A similar (yet different) problem is described here, I tried the solution proposed but it didn't work in my case.

Any clue?

Solution 1:

Somehow resetting NVRAM solved the issue. I am still puzzled about the cause of the bug, but at least I got ssh working properly again.

Here is a link to an Apple help-document on how to do this: https://support.apple.com/en-us/HT204063