Hi a 500 error is a general internal server error message telling that the server could not process the request.
Please provide some more information.
Do you have a php error_log ?
Also does exception and system.log in /var/log provides any useful information ?
I enable developer mode in index.php and nada in exception, system or php error logs. However when enabled jscript console shows nothing and continue stays on billing section rather than redirect to cart. When developer is not set jscript consoel gives ...
[Error] Failed to load resource: the server responded with a status of 500 (Internal Server Error) (saveBilling, line 0)
Further debugging in devtools..
Shows POST mydomain/checkout/onepage/saveBilling/ 500 error in prototype.js:1530..
Billing.phtml sets up that url as the on click on continue from the billing step.
At this ;point my jscript skills run out and and I can't work out why the saveBilling url is being setup.
May I ask what kind of payment provider you have enabled?
This error has been related to some payment methods like Amaszon, and alos earlier year it was a conflict with Supee-7405 etc.
What Magento Version did you upgrade from ? You have upgraded one version at the time (not missing any one) could be there is something not upgraded right. Please advice.
Paypal. and express is working fine i.e when the checkout steps are bypassed.
The upgrade was CE18.104.22.168 to 1.9.4 . The symptoms certainly "smell" like a bad upgrade. So unless i get another idea I am going to downgrade back to 1.9.2 and bring forward in smaller steps.
I downgraded to 22.214.171.124 and all works as expected.. so something in the upgrades broke. Il bring the site forward in baby steps and see where the culprit is.
I am also getting the same issue with PayPal Plus module.
Can anyone suggest the solutions for the same?