I may regret asking this, but what IP address does the Pi think it has, and what IP address does your PC think it has?
Chances are, both your devices are being NATted, which makes communication between them extremely difficult. My phone, on Vodafone here in the UK, is given a 10.* number, which is NATted, and I know most mobile networks worldwide do the same thing. Your fibre ISP may issue you with a proper IP address, but that'll be on their side of your home router, with that router also NATting. As the carrier is doing the NAT, you can't put a port-forward in to allow inbound connections to the Pi, and although you may be able to do something similar on the PC, that will involve installing some sort of ssh server on your PC (under Windows? Don't ask me how -- I don't use it), and getting the Pi to poll once in a while.
NAT sucks. CGNAT sucks at carrier-grade levels.