Just becuase there is one shown close by and typically with a nice ideal ‘coverage’ circle (a default setting in the console/map) that doesnt mean it can see where you are (building clutter, geography/topology etc. If you know approx location of the GW then take your node close by and test there…
…better yet invest in a cheap GW and add to the community coverage (e.g. TTIG, Dragino LPS8, RAkKetc…) that way you have more contol on your development activity (can see traffic on the GW console page etc.) and you contribute to the community coverage expansion 
If you post your approx. location some nice forumite might have a pop at predicting potential coverage (or not)! for you…