When i looked at Supervisor a day or two ago I saw that Supervisor needed to be upgraded from 5.9 to 5.10 and that Core needed to be upgraded to 2021.1. I went ahead and upgraded Supervisor first, and thought I then upgraded Core. Today I looked and, while Supervisor is at 5.10 as expected, Core is at 2020.12.7 and is NOT showing any upgrade available.
I researched on the forum and found a similar problem that suggested changing supervisor settings to static IP and adding another DNS address (126.96.36.199) might help. It didn’t.