Well this is where it gets complicated. Most likely, your
Blue Iris server's IP address is changing periodically, causing the port forwarding rule to become invalid. Running the remote access wizard creates a new forwarding rule for the new address and it begins working again ... until the next time the address changes.
There are a number of problems with this configuration. First of all, UPnP makes your network extremely vulnerable. Lots of IP cameras come with UPnP enabled so the moment they boot up, they expose themselves to the whole internet, and then those cameras get hacked. I know it sounds ridiculous but your cameras could very well be hacked and be part of a botnet already.
So step 1 is: Log in to your internet router (which is also your cable modem) and TURN OFF UPnP. Then reboot the router to make sure any ports that were opened by UPnP get closed.
Step 2: In your router, find the DHCP server settings. You need to add an IP reservation for your Blue Iris server so it always gets the same IP address from your router. If your router doesn't support IP reservations, then you will need to manually assign the IP address, subnet mask, and gateway on your Blue Iris server. This is pretty complicated for a newbie so hopefully you can do this with an IP reservation instead.
Step 3: In your router, forward a port to the Blue Iris server, with the destination port being whatever port number your Blue Iris web server is listening on. The source/external port can be nearly any number you want.
If you get that far, you should probably use whatever access restriction or parental controls your router has to disable internet access for each of your IP cameras. If they have indeed been hacked and made a part of someone's botnet, this should prevent them from calling home.
Thats all. If you can complete steps 1-3 then your Blue Iris server should be reliably accessible through the forwarded port.