Sip 480 error no user responding


Possible area code or dial pattern issue.
I’ve been calling WY,WI,AZ,CA,MT and AK. Today
ALL works great except 907 area code Fairbanks,
and Anchorage, AK.(I get Sip 480 error no user responding)
using ZOIPER softphone. Double checked the issue and
found problem isolated to 907 Alaska?


Many cheap SIP providers do not cover Alaska or Hawaii

thank you