Please look at the following points below to help resolve this issue: 

1. This could be the case if the original set up of the phones were set up to ring as a 'ring group' and one or more users have removed their phone line out of the ring group - please confirm if this is the case. 

2. It can occur in a ring group set up if a user has diverted their line to their mobile as they are out of the office or on holiday.  

3. If the line is not put back into the ring group once the user is back in the office or from holiday then it will not ring with the other phones.  

4. Always remember if you change the lines to be diverted elsewhere you MUST always put them back to the default setting.  

5. Good Practice is to make a note of what the default phone configuration setting are BEFORE making any changes.  

6. Take a screenshot of the phone line configuration inside the Phone icon of your CRM account - using the keys Control + PrtScn for ease and then you have a MASTER to refer back to.

7. Is there an error message on the phone(s) that are not ringing when an incoming call is received?  Please contact our Support Helpdesk with the details of the message so that we can resolve this for you. 

8. Is the phone(s) registered to the incoming line to receive calls?  Please check to see if the phone line is off line and if you need to register the line to the phone by clicking here.

9. If a phone or phones are not ringing for incoming calls - instead only one phone is ringing as 'default' this could be a router setting called SIP ALG on your router which may need to be disabled which can then resolve this issue.