I’ve noticed that some Chrome ad-block extensions don’t work well with some Velo elements/functions.
But if it does not work on Incognito mode, that’s probably not the case.
Can you ask the client to open the browser dev tools (F12 key), and see the errors on the console tab? Maybe it will help to figure it out. Anyway, it’s a question for Wix Support team. and you probably won’t get the answer in this forum.