I have 13 soundpoint ip 501 phones

Makes sure your Firmware is all upto date. Had the same issue with the soundpoint ip 501.

If your phone isn't on a constant reboot cycle and can boot up, then go into Admin Setting and do a Format File System reset. NOTE: Only try this if you know how to download the software files onto the phone via FTP server. Once you download the latest software your phone should be almost as good as new.

Are you using config files loaded from the server? If so, make certain they are properly configured. Also, make certain the phone does not already have an alternate configuration in it that points elsewhere...

Check if the switch uses active or passive PoE and the volts it pushes out

Active(PINS)1 2 3 4 5 6 7 8RX/DC+ RX/DC+ TX/DC- n/a n/a TX/DC-
Passive(PINS)1 2 3 4 5 6 7 8RX RX TX DC+ DC+ TX DC- DC-
Cat 5 cable9V < 30m cable length12V < 60m cable length
Max Ethernet cable length is 100m

You need to reinstall all the files back onto the phone. You can get the files from the Polycom Website. You can also follow the instruction from my Polycom 501 Fixya blog to see how its done.

need to buy one soft keys station and that will connect to your master's.

Due to the age of the SoundPoint Pro, it some of its features are not compatible with newer phonesystems, such as CableVision. There are no software updates for the SoundPoint Pro, and as long as the Caller ID is enabled there are no other settings or adjustments that can be made to workaround these kind of problems unfortunately. I recommend contacting your service provider to see what kind of caller ID signaling they are using; most likely they will be using a newer digital system, or MDMF which is not backwards compatible with SDMF or earlier CID receivers.

I think you have to have the upgraded cable modem with the rj11 on the back in order to pull the voip dialtone. Hope this helps

As you have probably found, SIP phones are not supported until R5, which just came out.

Ohh this mean, you did not register this extension on your phone system. Create this extension on your phone system. Be sure that password given on Phonesystem is also configured on phone too.