Hik-Online is closing, Hik-Connect is not compatible with my device

Which one do you recommend?

Just use Dyn - they will provide you a free account, however you need to sign in every 30 days at the physical site to keep it active, or look for a promo code and snag two years for like $40 which will also get you numerous other features.
 
I'm using Dyn now but can't get iVMS-4500 to work. Before HikVision decided to terminate their original DDNS service, I was using that successfully with iVMS. In the app, I don't know what settings to use. Is it "IP/Domain" or "IP Server"? For the former, it asks for address and port. For the later, server address and identifier, whatever that means.

My routers update Dyn's DDNS settings, but I can no longer use iVMS.
 
I'm using Dyn now but can't get iVMS-4500 to work. Before HikVision decided to terminate their original DDNS service, I was using that successfully with iVMS. In the app, I don't know what settings to use. Is it "IP/Domain" or "IP Server"? For the former, it asks for address and port. For the later, server address and identifier, whatever that means.

You need to put IP/Domain on iVMS-4500.