Some devices connect to WiFi but cannot access internet

[Niceboy91]

Hi folks, have called EE about this, and asked a few friends for advice, so far no one seems to know what's going on.

I have a Huawei 4G router, into which I have inserted an EE mobile SIM on a plan with unlimited data. Some devices - a phone, two laptops, a tablet - are able to connect to the internet no problem. Other devices are having issues:
- Nintendo Switch connects to the Wifi but is unable to access the internet
- One phone has no issues; the other connects intermittently. It will be working fine but then drop off - I remain connected to the WiFi but don't have internet access, or have switched to my phone's 4G with no warning. This is usually temporarily resolved by disconnecting then reconnecting; or by resetting the router
- Got a new smart TV with different streaming apps - YouTube and Amazon Prime are working, but Netflix, iPlayer, Channel 4 and Apple are not, citing connection issues. 

I have no idea what's going on. Anyone able to offer any insights or potential solutions? Much appreciated!

[XRaySpeX · Accepted solution]

It might be an EE IPv6 issue. EE has introduced IPv6 on its mobile network, but it doesn't fall-back to IPv4 nicely. Can you change the Profile/APN on your mobile router to APN Protocol = IPv4 only?