Sadly, this is a potential problem for any such app. Google doesn’t want to allow downloads of videos, and they frequently make changes that break these apps.
Looking at the publisher’s download page, I see that there are two different apps:
- “4K Video Downloader” was last updated in January 2025 and has a system requirement of macOS 12 or later.
- “4K Video Downloader Plus”, which was last updated on April 13, 2026 and has two releases - Apple Silicon and Intel (macOS 12+).
It seems clear that they stopped work on the original app about 1.5 years ago and moved to the “Plus” version. Since I’ve never heard of this tool before today, I couldn’t begin to speculate why.
So it looks like you’ll need to get the Plus version, which might require getting a new license.