"Endless Runner" disappearing map

Hello everybody!
I’m very new to Unreal Engine and I’ve decided to follow the “Endless Runner” tutorial to gain first experience.
Everything were more or less fine, but then I’ve come to this moment:

more exactly to 5:03 - moment of testing the map with floor tiles and rocks.
I expected to see some results, but I see… nothing. After clicking “Play” nothing appears - like all the project elements disappeared.
There’s only empty space :frowning:

There was also a problem with Box Collider in the first part - it wasn’t working, but the moves were proper.

My question is - what might had gone wrong? I was checking the video several times and I have completely no idea what to do now.
I have the level saved as “RunMap” in “Maps” catalog.

I’m using Unreal Engine 4.8.1.
I’ll be very grateful for any help!

I’ve solved the problem myself - from unknown reasons the editor must be working with Administrator privileges, otherwise the saved project won’t work properly.
I have no idea why it works like that.

I’m having a similar in 4.9 on part two I’ve redone tutorial several times but when I hit play simulation nothing spawns, I’m new to unreal what is Administrator privileges?

I found this tip on youtube and it got me working.

"Make sure you set the default game mode to “RunGameMode” and the default map for editor and game to “RunMap"To do this go to settings while on RunMap and click Project Settings, then go to Maps and Modes”.