Hey there supertoaster,
That is an odd symptom to be stuck unable to find a match only when on mobile data. I have heard of issues like this though in relation to T-mobile and Sprint. It has to do with how the game handles IPv6 and the mobile provider doing it a bit differently than expected. It is considered a known issue. We have some workarounds that most players can do in our known issues forum thread here.
Note there’s an expandable section in the above post that gives that workaround.
Hopefully this helps out. Cheers!