Get-ADUser is not recognized

Why it happens

The AD cmdlets live in the ActiveDirectory module, which arrives with the RSAT feature rather than with PowerShell itself, so a plain member server has no copy to auto-load. Auto-loading only searches the directories listed in $env:PSModulePath, which means a module installed elsewhere stays invisible even with the files present on disk. Server Core images and containers frequently leave the feature out altogether.

Check this first

Working through it

1. Run Get-Module -ListAvailable ActiveDirectory and see whether anything comes back at all.
2. Install the feature if the listing is empty: Add-WindowsCapability -Online -Name Rsat.ActiveDirectory.DS-LDS.Tools on a client, or Install-WindowsFeature RSAT-AD-PowerShell on a server.
3. Call Import-Module ActiveDirectory explicitly and read the error, since a version mismatch reports differently from a missing file.
4. Inspect $env:PSModulePath for the directory holding the module when the files exist but the listing came back empty.
5. Confirm the console architecture matches, because a 32-bit host process cannot load the 64-bit module.

Avoiding it next time

Verify the repair: After installing or exposing the supported tools, verify Get-Command Get-ADUser and run a limited authorized read query.

Primary documentation

Active Directory PowerShell documentation