HI @KWT2023
One solution is to clear your browser cache and cookies and try uploading your data file again
Since you mentioned that tech support hasn't been helpful, you might try and Clear your browser's cache and cookies to ensure that any cached data isn't causing the issue or try using a different browser or device to see if the issue persists.
you should also Review the Upload Process and Double-check the data upload process to ensure there are no issues during the upload itself.
also maybe check the data format in some case.. a possibility i guess
If still you feel like issue ain’t resolving try reaching out to Qualtrics Support once more,
Are you using a VPN? I sometimes receive error messages across Qualtrics when I’m logged onto my work’s VPN.