Although you created the GC on the new server you must make sure that you transfer the FSMO roles also. check this site: Transferring FSMO Roles.
And here: Moving FSMO roles from one DC to another DC.
this should help. let us know if there are any issues.
In addition you also probably need to configure the client machines to use DNS on the new servers IP address instead of the old servers IP Address (Assuming that the old server was your only DC). You also need to make sure that DNS is setup on the new server before you can do this.
In addition to FSMO roles for a domain controller, you need to consider that you are also retiring the first exchange server in your organization. Here is a link to Microsoft’s KB article on how to do this task that must be done to make everything work properly, this KB article is numbered as KB822931.