Sorry for hijacking this thread but I have the exact same problem . I just bought the F-16 module and when I want to install it it gives me the same error.
I did the above ;I see that the installed version is with the .1 but still the error that Version 2.5.6.59625.1 is not available.
00000.000 === Log opened UTC 2021-01-23 14:12:10
00000.302 INFO : DCS_Updater/2.7.3.52 (Windows NT 10.0.19042; Win64; en-BE)
00000.302 INFO : cmdline: "F:\Games\DCS World OpenBeta1.5\bin\dcs_updater.exe" --apply install F-16C
00000.307 STATUS: Initializing...
00000.327 INFO : basedir: F:\Games\DCS World OpenBeta1.5
00000.327 INFO : dcs_variant.txt: openbeta
00000.327 INFO : DCS/2.5.6.59625.1 (x86_64; EN; WORLD,A-10C,FC3,CA,KA-50,RAZBAM_AV8BNA,F15C-THE-GEORGIAN-WAR_campaign,F15C-REDFLAG_campaign,NEVADA_terrain,PERSIANGULF_terrain,FA-18C)
00000.327 INFO : branch: openbeta
00000.327 STATUS: Connecting to update servers...
00000.620 INFO : Got reply from www.digitalcombatsimulator.com
00000.713 INFO : Got reply from www.digitalcombatsimulator.com
00000.715 ERROR: Version 2.5.6.59625.1 is not available.
00002.433 === Log closed.
this is my auttoupdate.cfg :
{
"WARNING": "DO NOT EDIT this file. You may break your install!",
"branch": "openbeta",
"version": "2.5.6.59625.1",
"timestamp": "20210103-135253",
"arch": "x86_64",
"lang": "EN",
"modules": [
"WORLD",
"A-10C",
"FC3",
"CA",
"KA-50",
"RAZBAM_AV8BNA",
"F15C-THE-GEORGIAN-WAR_campaign",
"F15C-REDFLAG_campaign",
"NEVADA_terrain",
"PERSIANGULF_terrain",
"FA-18C"
],
"launch": "bin/DCS.exe"
}