Use your electronic identity card on the web
Windows sometimes marks files downloaded from the internet as "blocked", separate from the SmartScreen message shown during install. This happens by default for any downloaded file, not just the beID Helper.
Windows adds an invisible attribute ("Mark of the Web") to any file that arrived via a browser. While that attribute is present, Windows may be extra cautious on open — for example, warning that the file "might be harmful" or refusing to run it. This is a generic precaution applied to all downloads.
Re-download the installer directly from beid.hermesplatform.be/download — an incomplete or interrupted download causes similar error messages. If a SmartScreen screen still appears after unblocking, see Windows blocks the install (SmartScreen).