I can't provide any information of things because this makes absolutely no sense WHY this is happening.
If it doesn't work, then there must be a problem.
Nothing is perfect and errors can occur without making any changes yourself.
Although 95% of computer problems lies with the user.
Anyway, if you did forward your ports, did you set a static IP on your pc?
If you didn't, then your pc got a new IP and your router still tries to send data to your old one.
Maybe try using a program like Hamachi and setting up a LAN server.
Hamachi connects your friends and your network to seem like a local area network.
Of course this is not a permanent sollution, but if it works then we are closer to a permanent sollution