Access through firewall

I have a mycould ex2 ultra at home and working great. I added a second one to my account for a friend at his office, made myself admin and can see it from home on my account. However I can’t access any shares etc. When I set it up I invited him to have cloud access and could see it through cloud account, now I think I didn’t realise even though he accessed it through cloud account he was still accessing lcally as on same lan via wifi and his firewall is blocking seeing anything remotely?

If I am correct can i set it up through his firewall, external IP is dynamic but mycloud has internal static IP, I am guessing I can just port forward a port from wan to intenral static but what ports are required ( For the login and file access, port 9000 and port 10080 I believe) anything I need to do on mycloud itself and will this work? Thank You in advance

@DAK68

Online User Guide and Solutions for My Cloud OS 5 (wd.com)