Atlas map connection is broken

So I have two maps connected by the dotted line on my atlas map. Hidden Grotto map is complete and is green. The Sulphuric Caverns on the other end of the line in pale and inacsessible as if I haven't completed any map connecting to it. I tried to mouse-click inbetween the two as sometimes map nodes are covered with terrain and there might have been some hidden map preventing me to acsess the one that I want but that's not the case.

bump, i have multiple cases on my atlas where i cannot the connected map