You all should stick to testing the client & server with a launcher instead of Play in Editor. Most things work that way. Even if you get login to work inside the editor, it will just do logging in once, and after that you have to restart the whole editor. To fix this, you need to create .bat / .sh files to launch the Editor, and the project with -client / -server and use them.
Example .sh I’m using:
/Users/Shared/Epic\ Games/UE_4.27/Engine/Binaries/Mac/UE4Editor.app/Contents/MacOS/UE4Editor /Users/Shifty/Documents/Unreal\ Projects/MyProject4/MyProject4.uproject MainMenu -game -clientonly -ResX=1280 -ResY=720 -WINDOWED -log
You can do the same thing with server, just change the -game -clientonly to -server. The MainMenu is the name of the map it should load - beware, even if you set the project settings to default a map, you should set the client to the main menu here, and the server to the map of your game for it to work properly.