Hi,
Our outlook client suddenly stopped working for all users this morning and all the buttons are greyed out and we are getting the following error:

Our CRM is on Update Rollup 18 (KB2958724). We are getting the same error for entire CRM and for all the users in both the outlook versions (2010 and 2016). Though CRM is working fine in web. I have gone through all the solutions available online but they are the fixes specific user and for specific entity. But here my issue is for all the users and entire CRM. I checked with my event logs and got following error details :
Faulting application name: Microsoft.Crm.Application.Outlook.WebFormsHost.exe, version: 5.0.9690.4376, time stamp: 0x541cc7f0
Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000
Exception code: 0xc0000005
Fault offset: 0x04fb9134
Faulting process id: 0x1e3c
Faulting application start time: 0x01d343fed97829a9
Faulting application path: C:\Program Files (x86)\Microsoft Dynamics CRM\Client\res\web\bin\Microsoft.Crm.Application.Outlook.WebFormsHost.exe
Faulting module path: unknown
Report Id: 63526ea8-46c0-459b-9700-509013d7c859
and another error is:
Application: Microsoft.Crm.Application.Outlook.WebFormsHost.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
at Microsoft.Crm.Application.Utility.OutlookClientContextFactory.OutlookContext()
at Microsoft.Crm.Outlook.Services.WebFormsHost.Program.SetupClientContext()
at Microsoft.Crm.Outlook.Services.WebFormsHost.Program.Main(System.String[])
Can you please suggest any possible solution which can help me out of this issue?