Licensing Error

Suddenly Proget stopped working on our Build machines.

c:\Program Files (x86)\NuGet.CmdLine>nuget list -allversions PinForce.Database.B
usiness http://pf-build5:81/nuget/DCANuGet
Expected an absolute, well formed http URL without a query or fragment.
Parameter name: serviceRoot

Windows Application logs

Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 27/10/2016 8:00:58 PM
Event time (UTC): 27/10/2016 9:00:58 AM
Event ID: 70fc3cafc4e242a5a22ba1e1f00d1495
Event sequence: 2
Event occurrence: 1
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/2/ROOT-1-131220324553013677
Trust level: Full
Application Virtual Path: /
Application Path: C:\Program Files\ProGet\WebApp\
Machine name: PF-BUILD5

Process information:
Process ID: 2968
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE

Exception information:
Exception type: ActivationException
Exception message: Activation code is invalid.
at Inedo.ProGet.WebApplication.WUtil.Licensing.ValidateLicense()
at Inedo.ProGet.WebApplication.ProGetHttpModule.<BeginFirstRequest>b__9(Object _s, GetHandlerEventArgs _e)
at Inedo.Web.Handlers.DynamicHttpHandling.System.Web.IHttpHandlerFactory.GetHandler(HttpContext context, String requestType, String url, String pathTranslated)
at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, VirtualPath path, String pathTranslated, Boolean useAppConfig)
at System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Request information:
Request URL: http://pf-build5:81/nuget/DCANuGetDebug
Request path: /nuget/DCANuGetDebug
User host address: 10.1.0.218
User:
Is authenticated: False
Authentication Type:
Thread account name: NT AUTHORITY\NETWORK SERVICE

Thread information:
Thread ID: 3
Thread account name: NT AUTHORITY\NETWORK SERVICE
Is impersonating: False
Stack trace: at Inedo.ProGet.WebApplication.WUtil.Licensing.ValidateLicense()
at Inedo.ProGet.WebApplication.ProGetHttpModule.<BeginFirstRequest>b__9(Object _s, GetHandlerEventArgs _e)
at Inedo.Web.Handlers.DynamicHttpHandling.System.Web.IHttpHandlerFactory.GetHandler(HttpContext context, String requestType, String url, String pathTranslated)
at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, VirtualPath path, String pathTranslated, Boolean useAppConfig)
at System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Custom event details:

Product: ProGet
Version: 3.1.5

You will need to reactivate ProGet from the Admin UI. there will be instructions on how to do so within the software.