Getting error connecting to CRM Dynamics Online: An unsecured or incorrectly secured fault was received from the other party.

Our code is suddenly getting the exception below.

This was referenced in another post on here last week (Oct 15):

https://community.dynamics.com/crm/f/117/t/178881

Exception information:

Exception type: MessageSecurityException

Exception message: An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail.

Server stack trace:

at System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.ProcessReply(Message reply, SecurityProtocolCorrelationState correlationState, TimeSpan timeout)

at System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.Request(Message message, TimeSpan timeout)

at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)

at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)

at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)

at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)