How to reset Gmail so Mac Mail recollects all mail?

Mac Mail on Sierra stopped collecting Gmail on Wednesday, so I followed various instructions to delete the envelope files in Library>Mail>V4>MailData to force a rebuild (as the Rebuild menu item is completely useless – does nothing – why is it even there?).

Launched Mac Mail and it appeared in Activity Monitor to collected thousands of messages, but now shows only messages since Wednesday. If I restore the original envelop files, I have my old mail up to Wednesday only, and no more gets collected.

Log onto Gmail through web interface shows me that everything is there, i.e., pre- and post-Wednesday.

How do I get back to having both the old pre-Wednesday messages, and messages since Wednesday in Mac Mail?

Is there a way to tell Gmail (or Mac Mail) to actually rebuild the entire store – that is, download absolutely everything, and forget whatever arbitrary Wednesday threshold/pointers Gmail (or Mac Mail) has created?

(I have tried wiping out the entire contents of the Library>Mail, and that did nothing but get me to the same place of having no pre-Wed mail.)