@borzel

for information ! I have 4 servers different in hardware, installed the xcp-ng-7.5.0-2 version, used from localhost http://192.168.20.172/XCP-ng-Center.msi. I could connect to one as I could not to the other three. web XOA has connected to all 4 without errors. downloaded XCP-ng-Center-7.5.1.12, the problem remained.
Now I go to the forum, see link XCP-ng-Center-7.6.0.0-RC1 shake tested. All 4 servers are well connected !!!