Well that's weird. Those strings have been in every single pgAdmin 4 release, so at the very least I'd expect it to find the 2 installations you know are present.
OK, so those all look like candidates. The last one looks quite odd to me - I wouldn't expect to see a copy of it in there.
Any of them contain 1.5 as the version?
Please note, I'm going on vacation from this weekend and won't be back until ~17th August (though I may have intermittent access to email only; i.e. no laptop). If I don't reply to emails in that time, that's why.