Problem with AIM processing after moving to new hosting site

[BenTriangle]

Our AIM processing has worked fine on our previous hosting site.  This week we moved it to a new hosting site, and all of our transactions are coming back with the response pasted below:

3,1,6,The credit card number is invalid.,,[I removed the remaining info from the response]

The CC for this testing works correctly on the old site, but not the new host.  And we switched back to the old site to verify that it still works correctly - it does.

Oddly, the rejected transactions do not appear in the Authorize.net Unsettled Transactions.

I'm aware that AIM is now "deprecated", and I asked auth net support if moving the site would trigger something at Auth.net to disable AIM support for our site.  They were not helpful and suggested this community is where I should look for answers. 

Any insight from you would be much appreciated.

[BenTriangle · Accepted solution]

Thanks for the very helpful suggestions, Darrell.  In our trouble-shooting, we performed the steps you listed.  The thing that baffled me was that there were no entries for the declined transactions in Auth.net.  I presented that information to the Auth.net support folks and was told that there will not be transaction entries for declined transactions.  I knew from the response our new site was getting from Auth.net that it was indeed communicating with them.

As it turned out, even though all of the exposed configuration options were identical for the new and old website, the sites were handling encryption of the credit card differently.  Once I determined that was happening, I was able to solve the problem by changing a setting in the new site.  So things are working now, even though the new and old sites have this one different setting.

Bottom line, it was not a problem with Auth.net.

Again, many thanks for the reply.

Ben