I experienced this today, a couple of times.
I was in a no service area when I launched cachly and I could not get a position fix, may would not load (although I have off-line maps of the area). I launched another of-line map app (Pocket Earth) and it gave me my position. Back to cachly and no potion. I tried an offline list, still no position. A few minutes later, I came into cell coverage and bam, cachly gave me my position.
Later I went out of cell range (no service) and cachly seemed to give me my position, but cachly had been running in the background. I ended the app and restarted, again, no position.
Later I was in poor cell coverage, I launched cachly and I could keep touching the triangle in the lower right corner (localization) and it would not give me a position. I was driving home, still tapping the triangle. When I arrived home as soon as my phone locked onto my home WiFi, bam, I had a position.
The one clue I have is it seems to fail when in a poor/no coverage area and you do a fresh launch of cachly.
Screen shot 1 and 2 are in the no service/poor service area. Position would not show despite taping the localization button, lower right.
Screenshot 3 is when I got in better cell coverage and I was then able to get a position.
I'm running an iPhone 6S.