Missing "older" emails in gmail

Greetings:

Like many, I'm missing older emails in my gmail folders. Most folders are completely empty on my iphone, ipad and macbook air version of gmail, while daily activity is fine.

These older emails were not deleted or archived, merely moved to the folders.

I've tried all the techniques for searching with delimiters but nothing shows up.

I'm asking this group as research indicates this could be related to OS updates.

Gmail settings on Mac show IMAP is enabled and POP is disabled.

I'm getting beyond my skis. Could really use a fix here. Thanks!