Tried starting pgAdmin 4.1, observed that the menu bar came out as shown in the image below:
Had followed this guide on SO: Messed up pgAdmin 4 menu bar. Then uninstalled v.4.1. I now have v.4.4 installed but got same display.
Also, I can't get the object menu bar dropdown to work. Clicking it produces no response.
I didn't try opening the site using different web browsers (silly me). I had been using the default, Firefox Developer Edition.
Opening the pgAdmin web interface with Edge and Chrome opened it just fine. The error is specific to Firefox Developer Edition.