Sophos Heartbeat showing Red on XG but green on Sophos Central

I've recently upgraded to sophos advanced and 27/44 of my systems are showing 'at risk' or 'red'.

I checked sophos central and all the machines look well. I rebooted a few client machines and no change.

Here is an excerpt from the heartbeat log file on one of the 'red' clients:

2018-02-17T01:26:35.386Z [ 4340] INFO WinMain ----------------------------------------------------------------------------------------------------
2018-02-17T01:26:35.402Z [ 4340] INFO WinMain Starting version 4.3.60 of the Sophos Heartbeat service.
2018-02-17T01:26:35.402Z [ 4340] INFO WinMain ----------------------------------------------------------------------------------------------------
2018-02-17T01:26:35.386Z [ 4660] INFO ConfigMonitor::StaticThread The configuration monitor thread was started.
2018-02-17T01:26:35.855Z [ 5260] INFO ConfigMonitor::StaticThread The configuration monitor thread was started.
2018-02-17T01:26:36.558Z [ 5272] INFO RetryCalculator::Notify Connection failed.
2018-02-17T01:26:36.558Z [ 5272] INFO RetryCalculator::Notify Connection re-establish delay value is now 15 seconds
2018-02-17T01:27:06.684Z [ 5272] INFO RetryCalculator::Notify Connection succeeded.
2018-02-17T01:27:06.684Z [ 5272] INFO RetryCalculator::Notify Connection re-establish delay value is now 1 seconds
2018-02-17T01:27:06.684Z [ 5272] INFO RequestSender::SendRequest Sending login request.
2018-02-17T01:27:06.699Z [ 5272] INFO RequestSender::SendRequest Sending network request. Active Interfaces:
MAC: 34:13:E8:21:51:5B - INET: 192.168.20.99 - INET6:
MAC: B8:AE:ED:73:1D:A7 - INET: 192.168.0.149 - INET6:
2018-02-17T01:27:06.699Z [ 5272] INFO RequestSender::SendRequest Sending status request. Current status is -> health: Bad(3)
2018-02-17T01:29:06.773Z [ 5272] INFO RequestSender::SendRequest Sending login request.

Any help would be welcomed!