Router side if you do the setting in Virtual Server list and port forwarding list then it should be the router issue anymore.
Can you check your camera setting, make sure it is not in DHCP and it is in Static IP.
You need t make sure that your camera is using Static IP.
This is how i do my setting for the port forwarding.
The last thing is DDNS, try to get a free DDNS and try.
Since you have done the Port forwarding in the router , maybe you want to check whether your DDNS is still working?
Btw, my brickcom camera is also 4.5 years old.