If you could provide us more detailed information so that we can further investigate the problem.
1. What is the product and version?
2. Is this work before? If yes, what are the changes made before issue happen
3. Is this happening to all the apps or specific app only?
4. Is too many data you are exporting? If you tested a simple app and not much data export, is the issue still persist or not?
5. Please provide us more detailed information about slow (like example: 5mins to be exported and what is your expectation, did the expectation has reached before or not?) or when you exported to excel did you encounter error message, if yes, please provide us the error message or if not, will it generate only it is slow?