I've setup a new server and utilised SkateZillas DCS Updater. There's no AV and the Firewalls is turned off.
When I go to download a plan I get the following:
00000.000 === Log opened UTC 2023-08-07 14:41:12
00000.021 INFO : DCS_Updater/2.16.3.18 (Windows NT 10.0.20348; Win64; en-US)
00000.021 INFO : src-id: f697eb0b6959f621dddfde672932cdb00d183f23, lib-id: b88ea51ae2210987a3865f77cc1802548216d7a8
00000.022 INFO : cmdline: "C:\Program Files\Eagle Dynamics\DCS World OpenBeta Server\bin\DCS_updater.exe" apply f1d8406b-a577-4c29-8951-2f1e736ee272 5440
00000.135 STATUS: Initializing...
00000.296 INFO : basedir: C:\Program Files\Eagle Dynamics\DCS World OpenBeta Server\
00000.296 INFO : variant: openbeta_server
00000.300 INFO : Command: install FA-18C
00000.301 INFO : DCS/2.8.7.42718 (x86_64; EN; WWII-ARMOUR,SUPERCARRIER,WORLD,MARIANAISLANDS_terrain)
00000.301 INFO : branch: dcs_server.openbeta
00000.303 STATUS: Downloading version info...
00000.485 STATUS: Preparing to install FA-18C ...
00000.530 STATUS: Unknown module FA-18C
00001.761 === Log closed.