I had the same issue with A* making NO PATH, but after tuning global costmap inflation radius and cost scaling factor (decreased the inflation radius and increased scaling factor so that global costmap doesn't show too wide cost around obstacle), the error seems to be gone. Compared to the potential map I was getting when the error was there, I can see the potential map is generated in a more reasonable way. (connecting the start and goal position and not covering the whole map!) This is just another option you can try if you are having the same error.