Radius Server / Certificate issues

We are using InCommon as our Intermediate CA, which uses Comodo as its Root CA. We had a 3 year cert issued in 2015 with no problem. We renewed recently and are now having issues.
The cert is for a windows 2008 server running Windows Policy Server, which is Microsoft’s version of Radius. Since installing the new certificate, iOS devices are showing a message “Not Trusted” when trying to connect over WiFi. Android and Blackberry devices are not having the trust issue when connecting. We have tried installing two different versions of the Root certificate “AddTrust” and “UserTrust”.
I’m not sure if this is a server, client, or certificate issue, but any help would be appreciated.