Why is my export not working?

The export can be non functional due to the following reason:

Once the products export request is made, it will sent the request to queue to get the file. If the same user tries to export second file before the first one gets completed, then the export will fail.

How to over this?

Wait for the first request to complete to export second file.

Give it a time and try again in some time, if there is an error message.