User migrated to 2010 in resource forest and then needed to move back. Lync 2013 client worked fine while in resource forest but not once the mailbox rolled back to original Exchange servers in user domain. Lync configuration shows correct internal EWS URL. I even see 200 responses in the IIS logs, but the Lync client still cannot pull calendar information from Exchange. I see red exclamation points in the client saying Lync cannot communicate with Exchange server.
Had user try to logon to a different PC and same result, exclamation points.
I am curious why Lync is saying it cannot talk to Exchange when I know the EWS URL is correct and I see IIS responding.
User domain Exchange is 2007, resource domain is 2010.
Any ideas?