If it works fine on other networks then it’s your router provided by the ISP that’s the problem. If you can try setting 2.4 and 5Ghz networks to separate SSIDs with different passwords. I’ve got a couple of devices on my network that refuse to work if the networks are combined. You could try a different WiFi access point, an older unifi can be picked up cheap on eBay on if it’s just for testing. I was having similar issues with a Nintendo switch whilst working away, the hotels WiFi was just messed up