I have followed the steps at http://blogs.technet.com/b/exchange/archive/2011/02/16/exchange-2010-sp1-and-exchange-online-office-365-calendaring-faq.aspx to set it up, which seems to have worked, but I can't access the other organization calendar and they can't access mine.

I am using 2010 Sp1 on premise, the are on Office 365.

We'll need more to go on than "not working."

When a try to use the scheduling assistant the user from the other organisation shows as 'No information' -  same from their system to ours.

Are there logs I can look at?

There are several potential problems.  Searching the Internet has always helped me identify them.  I don't know if I can think of them all, but I've encountered malformed settings in the federation properties, WSSecurity authentication on the EWS virtual directory being wrong, firewalls misconfigured, and all sorts of issues with proxy and redirection within the organization. 

I've search for resolutions, but without some type of error code or message it hard to figure out. I even delete the relation with the Microsoft federation gateway and created it again, and recreated the DNS entries.

But still no luck.

Appears to be working now.

I ran:

Set-WebServicesVirtualDirectory identity "EWS (default web site)" WSSecurityAuthentication $true

Set-AutodiscoverVirtualDirectory identity "Autodiscover (default web site)"-WSSecurityAuthentication $true

then a iisreset

The interesting thing is running a Get-WebServicesVirtualDirectory |  fl before running the above commands it returned ExternalAuthenticationMethods : {Ntlm, WindowsIntegrated, WSSecurity} - meaning it thought WSSecuriry was already set but I guess it was mistaken.

• Edited by TrentQu 15 hours 32 minutes ago
• Proposed as answer by Ed CrowleyMVP 6 hours 5 minutes ago

I've certainly had to do that many times.  You're welcome to mark my post helpful since I directed you to t