I've recently joined a new payment system and they run via Authorize but I'm having issues when a payment fails.
It's running on MD5 Hash and I need to change/upgrade this but can't seem to sign up or generate a key.
I've tried phoning and the offices are closed during the stated opening hours by the pre recorded message.
Any help would be great, thanks!
You login to the Merchant Interface to create the key.
If you need to create a sandbox for testing:
Here is the Hash Upgrade Guide. It depends on which API you are using.