Hello,
Sometime, WRobot cannot create path (navigation files are created from default maps, some quests/events open the doors, remove/add the stones,..., this can happen also if it's narrow, or sometime without reason).
By sample, it is a narrow staircase, you get error like (navigation file tell at WRobot than he cannot walk in the staircase) (to get full pathfinding logs, in advanced general settings tab 'Path...' activate option "Server Logs")
(to get detailed log, you need to activate option "Show server logs" in advanced general settings tab "Path-finding").
Now, we will add offmesh connection (we will add staircase path):