Attachments to an assessment can not be uploaded from mobile browser since the 'Attach' button is not clickable. The functionality works instead in mobile app.
Steps to Reproduce
1. Navigate to Survey > View Survey
2. Open Customer Satisfaction Survey
3. Open the record from Metric Categories related list
4. In the 'Assessment Metrics' related list, click Create New
5. Type the name and Question and set the Datatype to "Attachment"
6. Submit the record
7. Navigate to the Survey Definition by navigating to Survey > View Survey --> Customer Satisfaction Survey
8. Click on View Survey URL and send it to a user through Connect
9. Open the mobile app(both iOS & Android), and using the link, open the Survey
10. Click the attachment icon, and try to add an attachment. (It will allow you to add an attachment)
11. Try the same thing from a mobile browser and try to click thr attachment icon.
12. This will open the popup where the "Attach" button is visible.
13. Click on 'Attach' and notice nothing happens.
Related Problem: PRB1280927