Originally Posted by RealHJ

When you pull up the reservation - on the website only, it will never show in the app - it should show you as "waitlisted" for the flight in question under a duplicate I-class entry for it. If it shows, there is a chance that it might have been done correctly.

In the past, when pnr.sh still used to work for UA, you could pull up the record via pnr.sh and you'd get the actual waitlist code, how it's entered (I think it's in the XML output, but not displayed on the website). That way you could see is it likely done correctly, if the collective wisdom on the various waitlist codes for various status levels is correct (it's been never confirmed, so we don't know for sure). But, AFAIK, that is no longer possible.

If it doesn't show as waitlisted when you pull up the PNR on united.com, however, then it is 100% certainly not actually done.