How do i re start my answer serviceon my sx-50 phone

Full 'make model (what it is)' needed. Here is your SX-50.

https://www.google.com/search?q=SX-50

Sounds like an 'Away from Phone' settings.

Google
make model manual
..

The phone line between the SX-50 console and the main control is disconnected or the console may need to be rebooted (unplug the phone line then reconnect it). If this doesn't solve it then contact your PBX system support person.

defective , replace or exchange

soooo don't answer the console

This is explained in the SX-50 system maintainer's handbook, 2 copies of which came with your SX-50 when it was new. However, this is a pretty old piece of phone equipment (30+ yrs) and when these systems were originally set up by outside service companies, it was not unusual for them to take the manuals so that customers would not be tempted to tamper and would call the service co instead. However, all is not lost. There is a very good Mitel support group on Tek-Tips (www.tek-tips.com) On tek-tips the Mitel forum is under Home->Forums->Wiring Closet->Phone Systems->Mitel Networks Solutions Forum. You will need to register in order to post. Hope this helps.

I have same problem on my sx-50 mitel consol, can any one solve this problem?

Negative, the SX 50 does not support CID. You can upgrade the Mitel or use a CID Multi line interface to a PC. Here is one such model.
http://www.callerid.com/

If you go to the bottom of the page on the right, click on how it works. Hope this hlpes.

You can switch to "night" mode on the console and the incoming calls should ring on the cordless. try it.