I have migrated a store from one domain to another, also a new server and also upgrade opencart from a very old version to the latest.
Everything looks to be working completely fine moving forward but displaying previous orders, customers and customer groups been causing me a few problems.
All orders, customers and groups are all in there but when i go to Sales > orders > Click view on a customer and then click edit I get "This page isnt working" HTTP ERROR 500
Any help on what the cause of this would be and steps to look at to try and solve?
Well, there are lots of things that can trigger a 500 error (it's sort of a catch-all). The first place to look on a new or updated system would be improper entries in .htaccess or php.ini, although if it's affecting only one page, it's unlikely to be that. If code was upgraded, there may be a PHP coding error some place. Look around for error reports and logged error messages (e.g., "error_log" files in various directories). You might have to ask your host how to enable these, if there are none. Look at the HTML source for the offending page itself (Ctrl+U on most browsers) to see if there's an error message in there. Here is a list of common 500 error causes: https://www.catskilltech.com/FreeSW/faq ... tml#err500 . Happy hunting!