Thanks for the links, however I had already checked them, and it didn't really help.
By the way, I have the game running fine on another computer, so I copied the installed folder on this one and the result is the following: At start the launcher stays on "Looking for updates" for about 40 seconds, then the bar goes off (I guess it silently goes into timeout): Launcher update
After that, if I put my credentials, the Play button activates and then it starts to check for game updates, but it fails with Launcher error: Code 987 RepositoryFileCheck_Error_MetaFile: Launcher error