My Program Files (x86) \
Opencpn 4.0.0 \ plugins \ weatherfax_pi
directory seems to have a small program 'PVW32Con.exe'
It also has a data directory with
coordinates.xml
weatherfaxinternetRetrieval.xml
WeatherfaxSchedules.xml
I will put PVW32Con.exe in the 4.0 Win PI folder.
for you to try putting that in the folder.
Please let us know if this helps for Windows users.