Can't make Boss Room tutorial work- Error with Relay namespace

Hi
I've got problem with starting with multiplayer Boss Room example.
Can't find similar problem with it on the net.
There are errors:
Library\PackageCache\com.unity.services.relay@1.0.1-pre.6\Runtime\SDK\RelayQoSService.cs(15,26): error CS0246: The type or namespace name 'IAuthenticationService' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.services.relay@1.0.1-pre.6\Runtime\SDK\RelayQoSService.cs(24,34): error CS0246: The type or namespace name 'IAuthenticationService' could not be found (are you missing a using directive or an assembly reference?)

Only thing which comes to my mind that can be connected is that I updated the Relay version in package manager from the current used in project to newest 1.0.0-pre6. I don't remember the version of the project. I also can't downgrade it to test the theory.

I'm attaching the visual studio reference codelines, which tells me nothing.
Is there something I can do ? The project version of Boss Room, which im using is 1.1.2 pre.