Unfortunately it is what it is.
My experience in a nutshell:
Looked in Dec: dates available in March for test site #1
Looked in early Jan: dates not available in March for test site #1 but test site #2 had availabilities
Looked in late Jan: dates not available in March for test site #1 and #2
So my advice is to look at the test sites further away, maybe you'll get lucky.
I already called to try and see if it would be different by phone and it was the same availabilities as online.