Hi,
Thank you for the details! However I could not find the language switcher button/link, I’m not sure where it is. Can you please link me to the french and english home pages, I will try it out.
Please note, that currently only WPML and Polylang are supported, so there is a chance that it might not work as expected. This issue sounds like a permalink thing, perhaps the ajax handler URL is somehow changed, where it shouldn’t be, I am not sure yet.