Port Authentication w/RADIUS

Hi,
I've got a number of GS728TP managed switches which I am in the process of setting up Port Authentication. I've got a Windows Server 2012 R2 system running Network Policy Server, and one of the GS728TP switches as I'm using as a test switch.

I've got the computer side of things authenticating properly, however we've got Samsung SMT-i5230's that I cannot get to authenticate.

I've given the phone, a username and password (which works on a test laptop), however on the phone it doesn't work. I've got the following information from Samsung:

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The system supports VLan Tagging 802.1Q and 802.1P

The authentication protocol EAP-PEAP is supported by the SMT-i5243,authentication protocol EAP-MD5 is supported by all of the SMT type IP Phones,
The configuration for the 802.1x feature is in the 802.1x submenu in the network configuration menu of the IP Phone.

802.1p allows for a Class of Service 0-7 to be assigned

The switch port that the handset connects to also needs to support 802.1Q/p

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I've checked the manual for the switch, and have confirmed that it supports 802.1Q and 802.1p.. However I'm wondering if I've missed something in the switch itself. I've included part of the log file below:

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09 May 2016 13:15:01%SEC-W-SUPPLICANTUNAUTHORIZED: MAC f4:d9:fb:53:25:d6 was rejected on port g16 due to wrong user name or password in Radius server
09 May 2016 13:15:01%STP-W-PORTSTATUS: g16: STP status Forwarding
09 May 2016 13:14:56%LINK-I-Up: g16
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I was using the same port to test my laptop, which was able to authenticate and I've got unauthorised clients setup to go onto a VLAN.

From what I have described, would there be a configuration that I am missing somewhere?