Here is my diagram
One physical server located at office as monitoring, and another is at client site
This two have connection/can ping. I already open specific port on client site (1024-65535)
Already tested telnet at port 2805 (it's working)
When I tried to add Client server at Veeam one located at our office, it stated "Veeam ONE Monitor could not connect to '10.254.1.38'. Access is denied. Please verify user credential and try again"
Welcome to Veeam Community Forums and thanks for posting!
Could you please make sure that the account you use for connecting has all the necessary permissions, please also doublecheck the credentials are entered correctly - these aspects should be checked first. If no luck, please follow the suggestions made by our support team and keep working with them directly on the case.