Please apply the following steps for this issue.
1. Download the reference material in the given assignment.(from the learner login)
2. Read the assignment in the given PDF.
3. Create the assignment as per the downloaded PDF.
4. Save it in the given format.(e.g. JPG, PDF.)
5. Do the learner login.
6. Upload the assignment.
7. issue will get solve.
If issue persists, please generate the SOLAR ticket with following details.
Learner Code-(those are facing issue)
Screen shot of the issue
Updated mobile number.