[lesserknowndan]

You should check the ‘whois’ information for the domain for the date it was registered. Here is a website to do this: https://www.whois.com/whois/

It can happen that an already registered domain will be apparently available but in reality something the website is querying fails to provide the correct information.

This has happened to me in the past, but checking ‘whois’ revealed the domain had already been registered and was active for a while.