HughesNet, Spectrum, T Mobile Home, and some others will cause that message. Sentinel uses FTP port 21 for updates, and some ISPs either block port 21, or have very high FTP latency times that cause that specific error. There are many posts in the forum about that, going back many years.
Spectrum has been known to intermittently cause that error. From reports here on RR, it does appear to affect a number of people using Spectrum, but only in certain areas of the country and not 100% of the time.... a lot of folks with Spectrum never have that problem.
You can check a number of those posts showing problems with Spectrum using this search link:
forums.radioreference.com
Something to try that others have used successfully as a workaround....... Set your smartphone as a hotspot, connect your computer to that hotspot instead of your home WiFi, and try the Sentinel update process again.