BUG #14707: pgAdmin4 does not start

The following bug has been logged on the website:

Bug reference: 14707
Logged by: Jaroslav Záruba
Email address: jaroslav(dot)zaruba(at)gmail(dot)com
PostgreSQL version: Unsupported/Unknown
Operating system: Windows 7, 64bit
Description:

I have installed the most recent version of pgAdmin4
(https://ftp.postgresql.org/pub/pgadmin/pgadmin4/v1.5/windows/pgadmin4-1.5-x86.exe)
Unfortunately pgAdmin does not start, or at least does not show any UI. I
only see the new (semi-transparnet) splash screen and then nothing happens.
When I click the splashcreen it just disappears. I can still see the process
in the task manager though, holding onto roughly 80-100megs of memory.
Every new attempt to run the app creates a new process with new splash
screen that does nothing.
I get no (visible) error message, and I see nothing in the Event Viewer.