Hey everyone!
I had this issue in UE4.20, and it might have been resolved in later engine versions, but I wanted to post this resolution just in case anyone is still using this version and had this issue. I didn’t see an answer for this, so if I’m sorry if I’m double posting.
The issue started when I set up a series of stream levels and added a nav mesh bounds volume to the persistent level. Unfortunately, one level already had a basic navigation system set up so my recast navmesh in the persistent level disappeared. I’m assuming this was the issue because it did not replicate after I created a new level without a navigation system, but I was never able to fix the original.
To resolve this I went into the world settings and disabled the Auto Spawn Missing Nav Data option. It was a pretty simple resolution, but it had me stuck for awhile trying to figure out why I couldn’t get the recast settings back.
Hopefully this helps someone!