This problem is also solved only this time I have no clue what did the trick.
What it was
not, that was the firewall.
For that purpose I had ticked every checkbox on to log every error or blocking.
After trying a lot off things I cleared the log file for the x-st time and after some refreshes there was suddenly the notice that SIP1, yes voxalot account, was trying to connect.
First there was a 401 error but the second attempt was good.
From that moment I can call true the Netherlands SIP Broker PSTN access number my ATA.
It is not must to help others but I am very pleased.
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