@Austin G Thanks. It is working for me. Problem solved.
I am having exact the same problem. On Evernote Web, the search simple does not work. It works only for notes added recently. For example, when I search in Evernote Web for "2017 IPTU", it shows me nothing. But when I search in Evernote for iPhone for "2017 IPTU" (same terms), it shows me correctly. I uploaded the attachments with the photos of each search.