Hi Mathew,
It doesn't make a difference because the resource I am trying to search doesn't have any booking so far but still the availability is showing as zero. This is a trial instance that I created for demo showcase with client
I did observer some changes here- first I was using a project that was created form a project template. see below screenshot for schedule & team members


Next I created a project record from the template and below are the results.


I generated the requirements for generic resources and tried to book resources- result is was able to book but had seen strange behavior with some random dates.

When i opened "specify pattern" and saw the resource requirements generated I found that start date & end date timings are wrong. It is showing from 12 AM to 12 AM, where this should be pulled from the project calendar i.e., EST 8 AM to 5 PM




After changing the start & end times manually it shows that resource is available; still availability of 8 hours is not shown completely. Sorry I don't have screenshots to show as I have modified some changes to the project and also resource are booked for other projects.
I faced the same issue in my previous trial accounts and I tried to reset, and created multiple times trial accounts and this was my third one. Microsoft tickets are still open by the way

To conclude this question, in my case there are some know bugs for version 3.xx and to make things work just edit the requirement record and click "Specify pattern" to see the bookings and correct them otherwise do not use project templates and just proceed with manual creation of project.