Remote access problem

I have been working with my ISP to fix the access problem from outside my network. It was working for a few months until something I think they changed. My ISP says I need to be able to specify the IP for incoming traffic in Plex. Is this possible? Right now I have port 32400 forwarded through my router and they tell me that they also have that port open however in my server settings my IP does not match what they say it is to be. I would be willing to pay somebody to help me figure this out otherwise no sense in having the "Plex Pass" Any help is much appreciated!