Sounds like you have lost the configuration - you may need to reboot the phone and reload the correct config and possibly the software which will point to the server...I am not a Voip expert so your best bet is to give Polycom support a call.
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The community's VoIP => FAQ <= contains this post here:
Sep 27, 2012 Question: I get the error Message “application not present / found” on my phones screen
Resolution: Please check => here <=
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Re: I also have these error message. It keeps on rebooting. Can you please provide me a way to get rid of this. My device is SoundPoint IP 331.