Error Message at Steam Startup

Game Version:

  • Build (17-Dec-2019)
  • Platform (Steam )

Issue:

When launching the game via Steam, a Window pops up (see screenshot).
“SteamAPI_RestartApplfNecessary() has been triggered. Aborting startup.”
Nevertheless, the games runs. What does this mean? what can I do?
Thanks in advance.
Age-of-Empires-2-Definitive-Edition_Error-at-Startup