How to re-install an Autocad 2011 Network Licence manager

Well, one of your biggest issues is that AutoCAD 2011 isn't even supported (oldest currently supported version I believe is AutoCAD 2015).

I have my subcription contract in order but Autodesk don't why to try a best offert on how to resintall it... They want me to install Autocad 2018 or something and really don't want to try to put in their head that when an employee is used to a version of autocad has as all the shortcuts and macros created, going to a newer version that bring NOTHING good is not wanted...

The reality is that if you want to be supported, you need to get to a supported version. I had customers who liked to stay with older versions, so what I did was that I had let them stay 2 versions behind the most recent. Sort of a happy compromise. Plus it should maintain reasonable compatibility with other companies you have to deal with.

Does anyone remember how to install an autocad 2011 licence manager (I think is is a flexlm or something).

It's the AutoCAD Network License Manager. It should be on your installation media (otherwise you'll be stuck downloading). But also, make sure that you still have your network license file. That's absolutely essential.

But once again, I will advise, upgrade your users to either AutoCAD 2016 or AutoCAD 2017. Don't try to simply go for the oldest supported version.

do you know if it can be get from the current server (somewhere in the folders...)? I have backups and access to all the previous files on it.

I guess I got the .lic files but the file start with SERVER srv-fs10 00XX0XXX0 (which is certainly his mac adress...).
I tried changing the name and mac adress but nothing

Tx.