Hi Moz, thanks for getting in touch. SFTP is just one of several methods of transferring files and if not in use (i.e. within a Scheduled Export configured to transfer a file via SFTP) can be safely ignored.
A 500 error could be a process timeout issue which can be as low as 30 seconds on some hosting servers. I’d also check the fatal-errors.log files within /wp-content/uploads/wc-logs/ or via WooCommerce > System Status > Logs > fatal-errors… for any fatal error clues.
Have a look at these resources for more information about the 500 error relating to bulk exports:
If this 500 error persists it may be neccesary to use WP-CLI to complete the export as that circumvents the timeout limit issue. Here’s a link to our WP-CLI documentation:
Feel free to open up a Premium Support topic if you require further assistance resolving this. 🙂