In the web/ subdirectory of the installation, you should find a file called config.py. Please create a file called config_local.py in the same directory, containing the following lines (excluding the ==== lines) :
====
from config import *
# Debug mode
DEBUG = True
# Log
CONSOLE_LOG_LEVEL = DEBUG
FILE_LOG_LEVEL = DEBUG
====
Then, try to start pgAdmin. That should create a more useful logfile in %APPDATA%\pgAdmin to share with us.