Help please

[Tanya]

Good morning, I need some help.
The following is something that is happening with 2 friends of mine, but it is only with these two.
When they get into my server a certain name (enumerating) message goes something like that.
I play DFXtreme and always open a server + host always serves for 6 people at maximum.
Even when there is a vacancy these 2 friends can not enter due to that message that I quoted.
Can someone tell me why they are getting such error?
Please help me solve this, because I have no idea why this happens.
Thanks for listening.