PowerShell: The 'x' command was found in the module 'y', but the module could not be loaded.

The 'Get-Thing' command was found in the module 'Thing', but the module could not be loaded. For more information, run 'Import-Module Thing'. comes from module auto-loading: PowerShell found the cmdlet in a module on $env:PSModulePath, tried to import it automatically, and the import failed. The message hides the real reason. Run the Import-Module command it suggests; the error from that command (execution policy, missing file, assembly conflict) is what to fix.

Reproduce it

A small module whose .psm1 fails while loading, placed on PSModulePath for this session:

$ErrorActionPreference = 'Stop'
New-Item -ItemType Directory -Path mods\Broken | Out-Null
Set-Content mods\Broken\Broken.psm1 'throw "Dependency Contoso.Core.dll not found"; function Get-BrokenThing { "x" }'
New-ModuleManifest -Path mods\Broken\Broken.psd1 -RootModule Broken.psm1 -FunctionsToExport Get-BrokenThing -ModuleVersion 1.0.0
$env:PSModulePath = (Join-Path $PWD 'mods') + [IO.Path]::PathSeparator + $env:PSModulePath
try { Get-BrokenThing } catch { $_.Exception.Message; '  -> ' + $_.FullyQualifiedErrorId }
try { Import-Module Broken } catch { 'Import-Module says: ' + $_.Exception.Message }

The 'Get-BrokenThing' command was found in the module 'Broken', but the module could not be loaded. For more information, run 'Import-Module Broken'.
  -> CouldNotAutoloadMatchingModule
Import-Module says: Dependency Contoso.Core.dll not found

The first message only says the import failed; Import-Module shows the error thrown by the module.

Typical underlying errors

Check what is installed

Get-Module -ListAvailable Thing | Select-Object Name, Version, ModuleBase
Import-Module Thing -Verbose

Several versions in different folders of PSModulePath are a common cause of confusion: auto-loading picks the highest version, which may not be the one you fixed.