Unable to load resources from module

[jeremyhagan]

I have installed this module and the ComputerManagementDsc module on my development machine. Both are listed in the same directory.

    Directory: C:\Program Files\WindowsPowerShell\Modules


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----        3/07/2024   4:49 PM                ComputerManagementDsc
d-----        9/01/2024   1:38 PM                Microsoft365DSC
d-----        9/01/2024   1:48 PM                ReverseDSC
d-----        4/07/2024   8:48 AM                SecurityPolicyDsc

However, when I run Get-DscResource, not resources from SecurityPolicyDsc are returned.

C:\Program Files\...\Modules> (Get-DscResource).ModuleName | select -Unique
ComputerManagementDsc
Microsoft365DSC
PackageManagement
PSDesiredStateConfiguration

Nor is the module listed when I run Get-Module:

C:\Program Files\...\Modules> get-module *dsc -ListAvailable


    Directory: C:\Program Files\WindowsPowerShell\Modules


ModuleType Version    Name                                ExportedCommands
---------- -------    ----                                ----------------
Script     9.1.0      ComputerManagementDsc
Manifest   1.24.103.1 Microsoft365DSC                     {Assert-M365DSCBlueprint, Compare-M365DSCConfigura...
Manifest   2.0.0.18   ReverseDSC                          {Get-DSCParamType, Get-DSCBlock, Get-DSCFakeParame...

And trying to import the module throws an error

C:\> import-module SecurityPolicyDsc
import-module : The specified module 'SecurityPolicyDsc' was not loaded because no valid module file was found in any module directory.

The only difference I can see between ComputerManagementDsc and SecurityPolicyDsc is that the former has a .psm1 and the latter doesn't. What do I need to do to get this module (and others like it) working?

$PSVersionTable

Name                           Value
----                           -----
PSVersion                      5.1.17763.5458
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17763.5458
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1