I have this annoying problem for weeks now... I talked with my mobile network operator's (MNO) support which is the Telenor-HU and with the Apple support too many times about this, but they couldn't help me. The problem affects many Telenor-HU iPhone users who updated their iPhones to iOS 15 and the MNO knows about this problem (they told me that they are already reported the issue directly to Apple, but Apple didn't fix it with v15.0.2 release). The problem occurs with both USB and Wi-Fi connection (for me), some ports are blocked by the phone's OS and Steam, Battle.net, BitDefender, etc... can't connect to their login and/or update servers on the PCs... I switched the SIM card to Telekom-HU with one of my colleagues and after that all the programs started to working well. I also put my SIM card to my old LG G8S and I had no problems with the hotspot. Conclusion for me: The problem occurs with just some MNOs (I think globally), but the problem is not on their side The problem came with the iOS 15 major update The problem affects the hotspot feature over Wi-Fi and USB connection too