I can't join my realm with my smartphone via wi-fi.
Joining the realm with 3g / lte is still possible.
I even forwarded all ports via my Router (FritzBOX) so that it was fully exposed to the internet with all ports open, but i still can't connect to my realm.
Switching to 3g / lte let me immediately join the realms server.
This may be related to issue REALMS-155.
I have the same problem, but in Japan.