Just earlier today we released the MyStyle Custom Product designer plugin for WordPress/WooCommerce version 3.9.1. This version has a bug fix for some pages coming back with a 404 response code, although the page would load fine. This resulted from updates to meet WordPress coding standards.
How to Update to 3.9.1+
Go to your WordPress admin > Plugins and press Update on the main MyStyle Custom Product Designer plugin. The update should be quick and painless!
Reactivate If Necessary
We have had reports that some systems deactivated the plugin upon update. If for any reason the plugin has an error while updating, it will deactivate. Be sure to reload your plugins page after update to check and re-activate it as the new version, verifying that it did update to at least version 3.9.1 or higher. In most cases this shouldn’t be necessary, but double-check just to be sure.