Murray Push Mower Won't Crank?

I have a Murray 21" push mower with a Briggs & Stratton engine, model year 2015. I've been using it fine for over a year. I keep it maintained: make sure the carb is cleaned, oil checks, nonethanol gas, etc.

I mow my grass every 2 weeks, aside from winter months, of course. Last time I cut my grass, it cut fine. Normally it takes 2 tanks to mow my lawn. I filled my tank the 2nd time to finish up and it won't crank. So, I figure I'd wait until next time, since, I didn't really have, but a couple of passes in the backyard.

Now, two weeks later, it still won't crank. I've taken apart the carb and detail cleaned it and checked it for any cracks or breaks. I know the gas is getting into it, because, I poured out gas when I took it apart. I've replaced the already fine gas with brand new gas, again, I use nonethanol anyway.
I've checked the spark plug, cleaned it off, it's fine. Checked the blade, cleaned it. Checked the oil, it's at a really good level. The pull string is at a fine tension, same as it was when I bought it. It tries to turn over, but just doesn't.