what is the clientIP in namecheap api request?

According to namecheap api docs, a request should have this structure:

response_request = f'https://api.namecheap.com/xml.response?ApiUser={ApiUser}&ApiKey={ApiKey}&UserName={ApiUser}&Command=namecheap.domains.check&ClientIp={ClientIp}&DomainList={DomainList}'

But I keep receiving Error Number="1011150" Invalid request IP when I input ClientIp as my IP address (I use a shared IP).

The ClientIp is:

• The public IP address of the system making the request. Google search for "What is my IP" for several services that will provide your public IP address.
• The same public IP address must be whitelisted. This link provides details on Whitelisting IP.