As macOS 10.15 phrased out all 32-bit applications and Garmin WebUpdater is a 32-bit application, it cannot run on my iMac anymore.
I have checked the Download page and it has not been updated since 2012.
I have been introduced to it by Garmin support team when I reported my Descent Mk1 did not alert on phone notifications.
I am afraid that I cannot solve a similar problem in the future when WebUpdater is required.
Please update it to a 64-bit application.