Try a pin hole / factory reset using this exact method ...
DO NOT DO THIS if the password on the base of the Hub is not legible or missing.
Instructions for Hub 3
Disconnect all unneeded ethernet cables from the rear of the Hub.
With the Hub Powered on use a paperclip or similar and do a pinhole reset.
Depress the pinhole switch for a timed 60 seconds then release.
DO NOT reboot the hub but allow it 5 to 10 minutes for it to boot itself up.
Once a steady white and no other lights are illuminated check your system again.
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BT Smart Hub 2 with 70Mbs Download,18Mbs Upload, 9.17ms Latency & 0.35ms Jitter.