[Mobile] Storage full

Hello, are you only a user of Adobe Express or do you have another Adobe program subscription, e.g. Creative Cloud All Apps, or Photoshop, or Lightroom etc.?

If you do use other Adobe programs then it's your storage across all apps that counts. Check all these locations for any files that count towards your storage limit:

https://assets.adobe.com
- check also the deleted files section https://assets.adobe.com/deleted (files are permanently deleted after 30 days);
https://lightroom.adobe.com
https://documentcloud.adobe.com
https://express.adobe.com/sp/
https://new.express.adobe.com/
https://assets.adobe.com/mobilecreations
- in the Mobile Creations area also check Deleted items.

Here's the help article about cloud storage and what is included as you may use other parts of it e.g. Libraries or Lightroom, that you haven't mentioned here:
https://helpx.adobe.com/creative-cloud/kb/file-storage-quota.html