Please attempt to clear the Cache in the app settings and confirm if you're still experiencing the issue.
To clear the cache, please take the following steps:
1. While in the IMDb app, go to the "You" tab on the bottom right-hand corner
2. Select the gear at the top right-hand corner, which will take you to the App Settings page
3. Scroll down to find "Clear Cache"
4. You will then be prompted to confirm clearing all application cached data
5. Select "Clear" and then try to login once again.