Why can't the admin connect via RDP to the server anymore?

Question

System administration

There is a remote server, there are several admins on it, and so recently 2 admins stopped connecting under their accounts (this window pops up) , despite the fact that for their PC under my account, for example, I log in freely, namely, they do not log in to any PC under their account I can’t for a reason unknown to me. (See the picture)
I really want to figure out what the matter is, and I ask for your help)
Thank you!

Answer 1

Good day. This was observed on the server under load - it was possible to connect from the second or third time. First of all, you need to look at what the server is loaded at this time.