There's no ball dropping here. There are specific criteria for an Amber Alert, and this case doesn't reach the threshold. The reason for the specific criteria is to ensure it's not overused, which then reduces its value. If every time a child went missing we did an Amber Alert, people would stop looking. They're rare, in part because they only use it (with rare exceptions) when there's a vehicle descriptor and a non-custodial, non-familial abduction.
Connecticut Amber Alert - Frequently Asked Questions
Someone asked about why they went inside the second time they were called to the house for a welfare check, but not the first. My guess is they knocked, saw nothing amiss at the front door, and left. Job completed. Second time around, someome maybe made sure to check all doors/windows, look inside as best they could, and either there was a force at another entrance or they could see mom inside. And then made entry and the discovery of the body.
Dad is 'cooperating' per LE. But they're very tight lipped about names, even moms. And I wonder if this is because without names we can't search court database. One theory in my head is they suspect dad, but they have him and not the child, and they don't want to jeopardize finding the child if she's being hidden, so they don't want him to feel backed into a corner, pressured.
I absolutely believe in my gut they have an idea of who has her at least, even if they aren't sure where.