Ok, looks like I was running an outdated version of the mod that simply didn't work any more…
But just in case: to make it work, select all the upgradable units you want help with in the order you want them upgraded and click the green button the mod adds on the top of the screen.

It sounds great, I found plenty how posts telling how great it is. Problem, no one ever explains how it works and I can't figure it out. I never manage to upgrade anything with this mod.
Could a kind soul unveil its secrets to the world, please?

It looks like it solved itself. I've no idea what happened. I would like to know, if possible, so that I can avoid it in the future.

I put the logs I found in that file.

https://mega.nz/file/T9MmGJAA#bgVlOX2sA9d519kti-s4y3xeV7uK1_apbwX82jVPkEc

No AV. I changed nothing since when it worked.

I played this morning. It worked well.
Then I got disconnected after putting the computer in hibernation. It didn't peep, just prevented from starting a game and displayed no public game.
I closed and restarted the client (and then the PC) to login back. The "environment" field is empty, with no choice available.
Any attempt to connect yields a "lost connection to server during login" message.
Any help would be welcome about how to fix it and how to avoid in the future.