[ACE] Error Extension not found. [Return Code: -1]

[Markypops]

Just installed ACE 3.18.1 through steam. When playing solo or joining my friend's server. The game always throws [ACE] Error Extension not found. [Return Code: -1]

I tried repairing, reinstalling the mods, and reinstalling the game along with the mods as well to see if it fixes it but it did not.

Here's a log that showed a warning that might help:

[ WARN] 22: InsituUgcModSynchronizationStrategy: System.ArgumentNullException: Value cannot be null. Parameter name: String at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) at System.Number.ParseUInt64(String value, NumberStyles options, NumberFormatInfo numfmt) at Utils.GameData.MetaCppReader.Helper.GetUint64(IEnumerable1 dic, String name) at Utils.GameData.MetaCppReader.Cast(ICollection1 keyValuePairs) at Utils.GameData.MetaCppReader.Load(String path) at Launcher.Extensions.InsituUgcModSynchronizationStrategy.DetectChanges(ExtensionInfo extension, String installDirectoryBySteam)

Thank you

[Numpty123]

I've got this problem as well, anyone got any ideas?

[Andx667]

I'm getting an error saying 'Extension not found...' when joining/starting a mission.
If you're on Windows 7 or Windows Server 2008, these operating systems are no longer supported as of v3.18.0. If you're not, it's probably a BattlEye outage and you'll have to either disable BattlEye or wait for it to clear up.

[Numpty123]

Thanks, I'm upgrading my Windows. Hopefully It will cure it.
Many thanks.

[artysta]

I have also had this issue. Disabling BattlEye in the Arma 3 Launcher (Battleye -> Enable BattlEye anti-cheat software Checkbox) fixed this issue on Windows 11 for me.