You can try the following solutions to fix an account that is not importing data:

1. Fully close and restart the app. To do this, follow the instructions for iOS and Android.

2. Remove the account, then reconnect it. To do this, select the account in Settings and press 'Remove Account'. You can then press 'Add Source', select the required account from the list and login.

3. Trigger a new sync. To do this, pull down to refresh on mobile, or clicking the sync icon on desktop. Wait for around one hour, as this is the maximum time a single sync can run for. Depending on various factors, including the amount/type of data being synced and the health of the service you are syncing it from, the process of importing content into your library can take up to one hour. 

If your account is still not importing after trying the above steps, please send us a bug report.