Hi, I am also having a similar issue. I track my teenager's location by signing into icloud -find my iphone and usually see her location just fine if her phone is powered on. But today, I am seeing a message that says "Online - No location available". I looked at settings in privacy/location and find iphone and they all seem to be on. I did not confirm that my teen is signed into their own apple account though. I am wondering if your question about one is signed on to their own apple account might be the issue. I believe that my teen might sometimes sign into her friends' apple accounts to track their locations, so I wonder if this might cause the message I am getting. What is confusing is if she is not signed into her own account, how would the cloud service know that she is online? Confusing...
Any more info you could provide on this subject would be appreciated.
Thanks,
Pinzrodads