When I click on the bookmarklet button after selecting text (in the RFI site) it sometimes sets my language as English, instead of French. When I then try to change the language using the upside down triangle I then lose the imported text. I can give more details if required.
There is sometimes an issue in the language recognition but it doesn’t happen very often. Please try it again. We do rely on Google’s language recognition tools for this feature so, if their tool isn’t working properly temporarily this can happen.
I have had this happen with a couple of sites. I think that there may be some invisible coding on the web page which is set to “English” when the body of the text (and in particular the bit you have selected to LingQ) isn’t in English.
I have found that a second attempt, maybe copying a smaller selection to the clipboard with fewer non-texty elements like headers and pictures, generally works.