Thanks to you and all the staff.
You're special!

So I must wait for a fix?
It's enough this ticket or I must open a new ticket?
Regards

As stated before, I think the problem is here:

Any news?
Regards

For now I don't want to try it.
The server on the instance is running correctly, the web server is accessible and working, so all my data are OK, I suppose.
I would like to know if the "Server refuse your key" error is related to the NFS problems, maybe my instance doesn't mount correctly the public keys partition or something else.
I can wait if it's a NFS problem.
Regards

I'm aware of the last key changes. After the key change I logged on bastion to confirm the fingerprint.

I log in through bastion host. I use putty under Windows. Setting are
unchanged.
I use bastion host through the command
"plink.exe bastion.wmflabs.org -l sbiribizio -agent -nc %host:%port"
I can log in to my other instance "osrm" with the same system, so it's not
a ssh key issue.