If your property doesn't have postal delivery, try to find a nearby address that does, then check that in Skinny's tool.
I had to resort to buying a Skinny sim to prove that I had 4G coverage (the map says zero coverage) and then getting help from LivingSkinny
My address shows the best signal possible on Skinny's own map. But I have phoned them and they tell me regardless of the map, they will not help me. My address is also showing the best signal on the Spark map. Skinny are telling me, despite a "best" rating on all the maps that I am not in their coverage area.
I have tried various addresses that show good coverage on the map in various rural addresses in Whangarei - none are serviced. Therefore, the only conclusion I can come to is that Skinny are not interested in rural customers. I am less than 15 minutes from the CBD for goodness sake. I feel pretty marginalised as a rural customer. We truly are second class digital citizens.
I have to say, I feel pretty pissed off by their attitude.