Disclaimer: I'm answering my own question.
I've just installed Postgres(version does not matter, I checked) and pgAdmin-4;
However, when I try to launch pgAdmin-4, it says 'Can't reach this page'.
I looked it up, tried everything, including pg_hba.conf, pg_dba.conf modifications.
The solution sounds really simple: Change your default browser to Chrome/IE(tried these). It does not open on the MS Edge browser.
I had it as default, since I was working on other html files, and didn't want them to interfere with Chrome tabs that were already open on opening those files.
Wasted a whole day on this, especially none of the signs pointed to a browser issue. Hope you aren't stuck on this!
If this does not work, you might want to look here: pgadmin4 : postgresql application server could not be contacted.
the error message on Edge
