"Team URL not found" on iOS app setup

I have the same problem. Can access the team from a browser on iOS fine but the app tells me "Team URL not found". I tried
"http://xxx.xx.xx.xxx/team"
"http://xxx.xx.xx.xxx/team/"
"xxx.xx.xx.xxx/team"
and
"http://xxx.xx.xx.xxx/team/"

all of the above resolve to the same error.
any ideas?