After porting from 4.19.2 to 4.20.1
I failed to package the game → Output log error suggested to change /script/engine.navigationsystem to /script/NavigationSyste.NavigationSystemV1
After I did the change I can not have any NavMesh at all…
(But I can package the project)
I tried to rebuild the navigation / delete and put new navigation bounds volume nothing works…
What now ?
What to do ?
Port to unity maybe ?
I am tired of all that pathetic UE4 changes that breaks code and even the editor…
I upgraded to UE4.20 two weeks ago and it was a real pain in the ■■■.
They changed most of the Navigation API, and I had to rewrite lots of code. However, they have a Python Script that performs the required changes on your code for you.
Check this out: Unreal Engine 4.20 Release Notes | Unreal Engine Documentation
And trust me, porting to Unity should never be and option. 
My code is perfectly compiles
The problem is the editor doesn’t generate any NavMesh when I am using a newer version.
If I’m using an old version it works perfectly fine - but throws an error on packaging the game.
Also why on earth would they touch navigation !?
It never worked as expected… so they decided to break it completely ?
Well Done epic!
Read the question…
I had exactly the same issue. Turned out I had to update the “Navigation Data Class Name” of the supported agent, because it was still trying to get the RecastNavMesh in the engine module (which no longer exists since they created a navigation module).
This can be done in the editor by going to Project Settings → Navigation System → Supported Agents and setting “Navigation Data Class Name” to None and then back to the desired class to trigger an update.
Alternatively you can also update the setting in your DefaultEnigine.ini directly. In my case I had to change “NavigationDataClassName=/Script/Engine.RecastNavMesh” to “NavigationDataClassName=/Script/NavigationSystem.RecastNavMesh”
Note: if you have your map open while applying this fix you might have to reload it.
I had to follow these steps to get it working.
I had it as dynamic since the beginning,
also your suggestion can be achieved easier I suppose - one can mark the navigation to always rebuild on startup and reopen a map.
Needless to say, but my problem was actually that navigation just didn’t build…
In case you wondering → no I didn’t solve the problem - and I didn’t try to go to 4.20 again…
I have a large project and it takes the whole day to try and port it to newer version.
And I am not interested in newer bugs - so…
this worked for me. thanks alot.
Thanks you!! THis Really helped!
>> This can be done in the editor by going to Project Settings → Navigation System → Supported Agents and setting “Navigation Data Class Name” to None and then back to the desired class to trigger an update.
That link is broken now. Here’s a working one:
Search for “PROGRAMMING UPGRADE NOTES”
Thanks! Work!