Note, I add similar problem (on Linux) for upgrading , on Plots, during half of day last Saturday (Nov 21st).
When I started to investigate, I found that in fact the update if the registry gor me with old entry’s : going to .Julia/registries/General /Plots/, and doing cat Versions.toml I saw last referenced version 1.7.1 whence I know it is 1.9.1.
Then I got all kind of unresolved references. It seems to me the registry was bad’ but a reinstall got me exactly similar invalid Plots versions in General. I check on other Linuxes that got updated the day before that that had indeed Plots versions to 1.9.1
In despair, I elected to wait some time and see if it was permanent or transitory. On Sunday a new ]up got me a correct General and all then since works.
I suspect the the European server for pkg.Julia Lang.org served me (incorrectly) an old registry version, is that really possible ?