Yesterday (11/07/2018) my son complained that none of his devices could connect to the BT wi-fi. All devices came back with the Authentication error even though nothing has been altered. Devices were his main computer using a wi-fi adapter, older 3g android phone and his netbook. My own phone 4G android had no problems connecting and nor did my wifes 4G android phone either. Tried my older 3G phone this morning and guess what "Authentication Error" so my guess is that something has happened to the hub, an update or alteration to the authentication protocol that older devices fail on. Has an update been automatically applied to the hub in the last few days? We use WPA2 security and have had no problems until yesterday. All devices can connect to our audio wifi network which also uses WPA2 on a different hub so it's got nothing to do with the individual devices.
Try a factory reset of the Homehub by pressing a pin into the recess button on the rear for about 20 seconds. This can often sort out problems.
You could also try changing the wifi mode from 1 to either 2 or 3