I know there was an issue with some Polycom firmware versions and 3cx though I 'm not sure which exact virmware releases. I'd first attempt to upgrade the firmware or use a known working version, also whomever you brought the phone from can usually provide support reseller, or distributor but actaully getting Polycom to assist isnt an easy thing to do.. This phone isnt supported (which isnt a big deal at all) will not find anything in the config guides from 3cx you can find the soundstation 5000,6000,7000''s I'd thnk they'd be a good starting point of reference. Error 0X20 is a config file error I've found some info on polycoms site that maybe of assistance see below.
http://community.polycom.com/t5/VoIP/501-phone-fails-to-boot-is-stuck-in-endless-cycle-of-failure/td-p/22112