What parameters are used for communicating successfully e.g. type of security credentials does your vendor require for accessing their system? Is it just basic (name & password) or mutual authentication (your client certificate)?
If the only change is that the vendor changed their server certificate, the things to look at are limited to a small scope.
If doing mutual auth, a change in the vendor’s cert has a couple of side-effects. The cert chain may not have the same CA in it as the old one. When doing mutual auth, the server determines which client certificate to present based off of the list of accepted CAs from the server. If your cert is not signed by one of those, no certificate is presented.
A little more information on how it worked before will go a long way in helping determine where to look.
Ed
#webMethods#Integration-Server-and-ESB#webmethods-Protocol-and-Transport