I hate to Necro this post, but it appears people are still having issues with this on Mobile.
In my situation I had to log into my character on the computer.
Home teleport to Lumbridge (a F2P location) and then log out.
I was then able to log into my account on Mobile, switch worlds to members, and teleport back to a member location.
After this my account acknowledged that i was a member, and this issue stopped.
If this does not work for you, and its been over 24 hours, submit a ticket through what ever means you can, since you cannot easily submit tickets for this and most issues.
@Mods: perhaps a link should be added in the Known Error Messages category in technical support describing methods to resolve this issue.
14-Sep-2020 20:12:46