Connection could not be established - for some users

[Achim.Z.]

Hello

I have a supplier that has access to ASG with his account.

When we test access to ASG from my computer it works correct.
After that we testet from his computer and got the error

"Connection could not be established"

When we tested from his computer with my account i also got this error.

First we thought, that is was caused by his computer, but we tried

Has someone an idea?

I am confused

regards
Achim