- If Develop is not in the menu bar, go to Safari > Preferences > Advanced and check the box “Show develop menu in menu bar”
- (Firefox) Go to Firefox or Tools in the menu bar, then Web Developer > Web Console
- Check this console for errors, specifically for a 403 error possibly related to AJAX
There are a few reasons this error could occur, such as plugin interference, host firewalls, and caching. Below are some steps that you can take to diagnose the cause.
To check if another plugin is the cause of the this issue:
- Disable all your plugins except WooCommerce and One Page Checkout. If the issue persists, then the cause is not interference from another plugin.
- If the issue is gone, enable the rest of the plugins one at a time until the issue is reproduced.
- Note which plugin caused the error and keep it disabled.
If the issue persists with only WooCommerce and One Page Checkout activated, it’s suggested that you contact your hosting provider and ask them if there is any reason why the hosting would block this AJAX call. Examples of these reasons might have to with security rules, firewalls, and permissions.
Caching on the page can also interfere with the AJAX calls. Ask your hosting provider if AJAX requests are cached and if there is a way to exclude specific pages from caching. If so, exclude the page that displays One Page Checkout.
If the issue persists and the cause has not been found, open a support ticket. Please include any steps you have taken for troubleshooting and the information gathered.