Update: now that Revise 3 has been released, this is no longer necessary. Just use fully-updated packages.
Several folks are having Revise problems that stem from Pkg installing a very old Revise version. You can fix it with
pkg> add Revise@2 pkg> pin Revise
For those who want the details: some of Revise’s dependencies have been upgraded in preparation for a Revise v3, but that release isn’t ready yet. Pkg’s resolver happens to notice that it can install newer versions of the dependencies if it goes back to an ancient version of Revise that didn’t have those dependencies.
This will be fixed when Revise 3 comes out, but for now pinning Revise seems likely to be the only reliable option.