Hi, what could be the reason for update fail 

Hello,
Just for your information, I moved your topic into the RDM Mac Support forum.
Regarding your issue, we had problems with the auto update in RDM 4.6.0.0, this is why you encounter the message below.
This issue has been resolved, however, in your case, you would need to download the latest version manually
https://mac.remotedesktopmanager.com/home/download
Best regards,
Jeff Dagenais
OKay, resolved