Hi,
We're sorry that you're unable to log on App, but in order to help you (and on support) we need you to be clear and provide as much info as possible.
We're a bit skilled on troubleshooting, but we can't guess things.
I'll give you some answers to most common situations:
Are you trying to log on this account?
A) Yes. Check if you're logging on Correct Version (World/Dutch)
A.1) How do I know that?
Android: At login you've a world symbol, tap on iot and adjust to the correct one
iOS: Go to OSM settings on iPhone settings/Apps and adjust the world there
B) No. Then try to log on the other account on web, if you're able to log on Web, go check reply A
If none of the above is the solution for you, please provide us all the steps you do, all the info required (not the password of course) and let us know where it goes wrong