If you are having issues viewing file content within the iOS application, it could simply be an authentication issue. One specific possibility is that Basic Auth is not enabled.
Resolution
1. Update to Liferay Sync iOS 1.1
2. If you are running version 1.0, add this line to your portal-ext.properties file:
auto.login.hooks=com.liferay.portal.security.auth.BasicAuthHeaderAutoLogin,com.liferay.portal.security.auth.CASAutoLogin,com.liferay.portal.security.auth.FacebookAutoLogin,com.liferay.portal.security.auth.NtlmAutoLogin,com.liferay.portal.security.auth.OpenIdAutoLogin,com.liferay.portal.security.auth.OpenSSOAutoLogin,com.liferay.portal.security.auth.RememberMeAutoLogin,com.liferay.portal.security.auth.SiteMinderAutoLogin