Emonpi update problem

Since installing a new BT wif-fi hub I’ve been having intermittent problems with the wifi connection to my emonpi - so I thought I would try updating the emonpi to see if that would help. However, the update log showed the update as failed. I have now lost all my nodes on the local emoncms (just showing as inactive). The emonpi LCD screen is showing “error: mqtt not connected” and the emonhub log shows “Connecting to MQTT Server - Unexpected disconnection”. The emonpi is however still sending data to emoncms.org OK. So looks like I have corrupted my installation. Any suggestions as to what to do next?