We have a membership form that has been working for several years. For some reason we are now getting a 404 not found error when submitting the form.
The url for the error 404 page is:
We don't update CiviCRM very often. Wordpress updates itself periodically.
Wordpress 5.5.1 CiviCRM 5.15.1
I've also tried deactivating every plugin, and using a different theme, and the problem still exists.