Problem with expl3.sty

[Phelype Oleinik]

Hi Gary,

On Mon, Apr 24, 2023 at 6:25 PM Gary Hoffman <glhoffman at gmail.com> wrote:
>
> ! LaTeX Error: Mismatched LaTeX support files detected.
> (LaTeX)        Loading 'expl3.sty' aborted!
> (LaTeX)
> (LaTeX)        The L3 programming layer in the LaTeX format
> (LaTeX)        is dated 2023-03-30, but in your TeX tree the files require
> (LaTeX)        at least 2023-04-20.

This error means exactly that:  your LaTeX format has expl3 2023-03-30
preloaded, but since you recently updated TeX Live, your installed expl3
is from 2023-04-20.

This error usually happens because TeX Live sometimes creates local
format files when updating, and "forgets" to regenerate them when
updating again.  The solution is usually to remove those local format
files.  See: https://tex.stackexchange.com/a/598609/134574

If you type "H <return>" at the error prompt, LaTeX will try to tell
you where that extra format file is, if it has some shell access.
Otherwise, you can easily locate the format file manually.

Hope it helps,
Phelype