A router or firewall is blocking qBitTorrent from getting incoming connections.
Not something you can fix in qBitTorrent since UPnP/NAT-PMP didn't help.
2) How do I know whether my router is blocking incomming connections?
As far as what I know I can see "qbittorrent" and the port in UPnP configuration of my router.
3) A point to note that my roommates who are using utorrent have no connection issues.
If you are certain that your router is forwarding port 15761 to the right LAN ip address (192.168.0.100 is your computer's?), then the router is most likely not the cause of your problems...unless it's conflicting with UPnP in qBT overriding the manual port-forward. Generally, if you manually port-forward UPnP isn't needed in qBT.
As for the firewall, I don't know if that works. Many firewalls when disabled just block unsolicited incoming traffic when set to OFF. That may not be the only firewall present, which can really make a mess of things.
You may need to test if qBT can work on one of your roommate's computers...then we can confirm the problem isn't qBT!
