I have configured calendar sharing, created a sharing policy, applied a user to that policy, connected as them in OWA, right-clicked on Calendar, chose Share and was presented with a screen to choose options for publishing the calendar. Once I click "Start Publishing" it pauses for a moment and presents the following error:

"Sorry! We're having trouble processing your request right now. Please try again in a few minutes."

A corresponding error in the event log is triggered:

Current user: 'HostedExchange.local/Organizational Units/{domain.name}/Test User'
Request for URL 'https://exchange.domain.name/ecp/Customize/MailboxCalendarFolders.svc/StartPublishing?msExchEcpCanary=wxdai2GrC0q6DJayoatadiv8tHYld9II37xXEAZO4KfdJSvNjNpY4sCUF2FJ3sMBBTbFlgQmgYc.' failed with the following error:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.TypeLoadException: Could not load type 'System.ServiceModel.Activation.HttpHandler' from assembly 'System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

I have also verified proper permissions on the virtual directories following this template: https://technet.microsoft.com/en-us/library/gg247612.aspx

Thoughts?

Found this article on Experts-Exchange http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_28418203.html

I modified the application pools to utilize .NET 2.0 instead of 4.0 and all is well and fixed.

Good luck!

• Proposed as answer by David Wang_Microsoft contingent staff 4 hours 5 minutes ago