Get visitors-list filtered by 1 uid shows no info

Hello

I was unable to find answer on my question.

I want to implement next scheme:
1. User landed on my site, press register button
2. On registration I getting Clicky UID from cookies, and query API to get more info about user:
https://api.clicky.com/api/stats/4?site_id=xxxxx&sitekey=yyyyy&type=visitors-list&uid=ZZZZZZ

Unfortunately I getting empty list without any data. Seems like there are time gap between this inforamtion about user stored in Clicky database.

If so, how I can make what I want? And how long it take to be able obtain to user's info?

Thank you!