Script do PowerShell para verificar o status de um URL

Semelhante a esta pergunta aqui Estou tentando monitorar se um conjunto de links de sites está funcionando ou não está respondendo. Eu encontrei o mesmo script do PowerShell na Internet.

No entanto, em vez de links diretos para sites, preciso verificar links mais específicos, por exemplo:

http://mypage.global/Chemical/

http://maypage2:9080/portal/site/hotpot/

Quando estou tentando verificar o status desses links, recebo a seguinte saída:

URL    StatusCode    StatusDescription    ResponseLength    TimeTaken
http://mypage.global/Chemical/    0
http://maypage2:9080/portal/site/hotpot/    0

Os links acima exigem que eu esteja conectado à VPN, mas posso acessar esses links pelo navegador.

Saída deInvoke-WebRequest -Uri https://stackoverflow.com/questions/20259251/powershell-script-to-check-the-status-of-a-url:

PS C:\Users\682126> Invoke-WebRequest -Uri https://stackoverflow.com/questions/20259251/powershell-script-to-check-the-status-of-a-url

The term 'Invoke-WebRequest' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

At line:1 char:18
+ Invoke-WebRequest <<<<  -Uri https://stackoverflow.com/questions/20259251/powershell-script-to-check-the-status-of-a-url > tmp.txt
    + CategoryInfo          : ObjectNotFound: (Invoke-WebRequest:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

$PSVersionTable

Name                           Value
----                           -----
CLRVersion                     2.0.50727.5472
BuildVersion                   6.1.7601.17514
PSVersion                      2.0
WSManStackVersion              2.0
PSCompatibleVersions           {1.0, 2.0}
SerializationVersion           1.1.0.1
PSRemotingProtocolVersion      2.1

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