Issue in making API calls to F5 LTM/GTM.

I can't see any attachment, please could you describe the error you are experiencing.

Not sure where the attachment got lot have reposted the same Lee.

How are you providing authorisation?

Can you try the following (replace admin admin with your credentials)

curl -X POST -H "Content-Type: application/json" -H "Cache-Control: no-cache" -d '{
    "username":"admin",
    "password":"admin",
    "loginProviderName": "tmos"
}' "https://your-bigip.com/mgmt/shared/authn/login"

Making this api call..

and access is controlled via cyberark for which a user has been already provisioned via AD.

If you haven't already authorised, you'll need to obtain the auth token and use the token in the X-F5-Auth-Token header in all subsequent requests. You could also use HTTP Basic auth an include the username and password in each requsts, but this isn't recommented

cURL example using X-F5-Auth-Token

curl -X GET -H "Content-Type: application/json" -H "X-F5-Auth-Token: QWERTYUIOPASDFGHJKL" -H "Cache-Control: no-cache" "https://f5-ip-address/mgmt/tm/sys/connection?options=all-properties&ver=13.1.0.4"