Since Mac OS Catalina arrived in 2019, HA has not opened because of Apple's Gatekeeper technology. After years without HA, I just found out how to bypass Gatekeeper. It involves changing the "quarantine" status of HA. It requires use of the Terminal application, (high level, risky, use with caution). Here are 2 websites which describe the fix. https://macresearch.org/fix-cant-be-opened-because-apple-cannot-check-it -for-malicious-software/
If you have this problem, please let the developers know that HA needs to be updated to meet Gatekeeper requirements. It involves registering as Apple Developer and getting the app notarized with Apple.
Il existe une solution est plus simple, sans utiliser le Terminal. Au premier lancement de l'application HA, après le refus de Gatekeeper, il faut aller dans le menu Pomme, Réglages du Système (anciennement Préférences), Sécurité, et donner l'autorisation à HA. Pourvu que ça dure !
In my case, "Allow" in the Security settings was not enough to open HA. I still got the refusal because Apple could not "check for malicious software" after completing the "Allow" step.
The two articles cited in my first post explain the method which worked for me.
I advise using the Settings>Privacy & Security>Security allowance to all as first step. Only if that fails, use Terminal.
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It involves changing the "quarantine" status of HA. It requires use of the Terminal application, (high level, risky, use with caution). Here are 2 websites which describe the fix. 
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