Hello Dan and Prokop,
so I have already solved the problem with loading arcgis AOPK services with our IT department.
The problem was that in our company we have a forward and reverse firewall, including a proxy, and it prevents (prevented) the required communication. I do not know the correct English IT terminology.
An exception had to be made for the communication to flow. On the arcgis services that worked, the exception was already granted in the past (eg ČUZK), although at that time it was not due to ArcGIS maps
Thank you for your willingness.
Kind regards
Michal