@HillFamily I’ll add a link here to a detailed explanation of the availability calendar.
I’ll now use myself as an example. I received an invitation today to sit for dates on my calendar showing where I showed I was available. However, for various reasons that are irrelevant here, I declined the sit and included a reply (promoting the forum, of course 
). I did not say I was unavailable, but rather only that I declined the sit. Even those who keep their calendar current, like me, will have reasons why they decline a sit.
I understand how it is disconcerting for homeowners who, in the past, have never had to consider actively seeking sitters. However, we have all seen how flexible we have had to become over the past two years. Sometimes so many things in life are not ideal but are also beyond our control. 