Message does not display

Hello,

The message indicating the amount remaining to have free delivery no longer appears when I add a product to the cart.
The Firefox console tells me this:
The use of “Mutation Events” is obsolete. Use “MutationObserver” instead.
You can easily reproduce the anomaly on https://mc12.fr.

I disabled autoptimize + modpagespeed on the server, but the problem persists (so I re-enabled these features).

Do you know what could be wrong?

thanks in advance