Lync Client 2010 unable to sign-in on Windows Phone 7.5

Ola,

Our users with Android and iPhone can connect to  lync mobile but our users with Windows Phone cannot.

I've found that the users with windows phone are getting this warnings from there phones :

2013-05-14 19:42:40.456+1 : Warning : 610016466 : HttpRequestPump : Got a WebException while reading the response for IssueWT.

2013-05-14 19:42:40.457+1 : Warning : 610016466 : SoapWebRequest : Found SOAP fault code {http://docs.oasis-open.org/ws-sx/ws-trust/200512}InvalidScope.

2013-05-14 19:42:40.457+1 : Warning : 610016466 : SoapWebRequest : Found SOAP fault string "The AppliesTo element of web ticket request points to a different web server or site.".

2013-05-14 19:42:40.457+1 : Warning : 610016466 : WebTicketManager : Found MsDiagnostic info in SOAP fault. Code: 28037. Reason: "The AppliesTo element of web ticket request points to a different web server or site.".

Any ideas ?

Thanks a lot,

Miguel Ângelo Saragoça Soares