Hello,
Given if FireRTC allows SIP URI calls; you should be able to forward incoming calls through your number via SIP URI – please note that you will need to contact FireRTC’s support firstly to see if they do allow incoming calls towards their network via SIP URI, and the correct formatting of that SIP URI for your account.
We see several call attempts towards the address "ravchaim@sip.firertc.com" however we are not showing any response from the remote system. As far as why, there are a number of reasons; firstly, as with the above mentioned, we recommend contacting FireRTC’s support to see whether they allow direct SIP URI calling towards accounts on their network.
If you have any other questions, please let us know