There are more people submitting, and if the system load is exceeded, the system will crash, so it keeps showing that it cannot be submitted. In addition, there is usually a deadline for submitting papers. If you submit it after the deadline, you will definitely not be able to submit it.
Find the reason and prescribe the right medicine. If you don't know the reason, you can ask your tutor and ask him to help you try. If it really doesn't work, you can try to contact the teachers in the library to reflect the problem and feedback your failed interface information and the results of the tried methods to them. They may have a solution.