Just based on what you are showing in the error message, it may be that the phone you are configured to use cannot be reached for some reason.
Check your phone configuration and make sure it is working properly.
Also, if you are familiar with SIP and analyzing network packets (and your phone is using TCP or UDP), then you can enable Protocol Capture on your Phone Trunk associated with the phone you are using and use Wireshark to read the captured SIP packets to get a better idea of what is going on. (If the preceding is not in your comfort zone, you will need to work with Support...)