Can someone explain message

[waydown]

Hi, I was unable to do port forwarding from a ZXHN H298N router. I had created a static address on my wireless network card. Also created a path on 'Application-NatLoop and Port Forwarding' on the router. I had reduced security on firewalls to minimum on both router and computer. I was using opensuse Leap 42.2. I was trying to open port 80 on my machine.
When I used 'canyouseeme.org' to verify if port 80 was open I got message: Error I could not see your service on 88.**.***.*** **on port (80). One reason why I was not getting port forwarding may be because I was behind more than one router. My external IP address was different from the IP address of the router. I read that if that was the case the internet facing router was with the ISP.
I wrote to my ISP and the following was their reply.

Since your site (building) has been migrated to CGN (Carrier-grade NAT), all the routers on that site (including the one located in your property) have CGN IP addresses. CGN implies that one public IP address is translated into several CGN IP addresses that we are providing to our residential customers.
The CGN migration is something that all providers in UK (and all over the world) started to implement for residential customers due to lack of IPv4 addresses.
The Static IP is available as an add-on and it is charged £5 per month. It can be added or removed from your account anytime and it is a temporary solution until we fully migrate to IPv6.
The IPv6 migration is happening as we speak and all sites should be migrated within the next 2 months. Should you wish to add the Static IP to your account, please confirm by replying to this e-mail.

Could someone explain what is being said in the message (I don't have a clue) or what I should do to resolve my problem. All help will be greatly appreciated.