Got a new used fridge that is "leaking". It has an ice maker but I didn't plumb it. After 48 hours I can't believe there was any residual water in the system.

Knowing nothing about refrigeration, I'm guessing there is a condensation pan that is busted? The room is air conditioned and humidity can't be that high, it's really comfortable in here.

Kitchen plumbing is fine, no leaks there.

Any thoughts on what the water pooling on my floor could be from?

take the access cover off the back and look at the tubing. if it was unplugged long enough for everything to thaw out then the drain tube from the freezer probably got disconnected somehow or is not going in the pan. If not then the drain is clogged, usually with ice.

Check the drain tube that sends water to the pan, they can get clogged with dust and back up.

This.
That's what l found. Took off the tube and cleaned it. Took care of the problem.

Tube with the orange arrow was not on right, so I fixed that.

But that frost-covered refrigerant line seems to be the problem.

Technician came out, said it had 10 PSI of refrigerant and should have only been 5. Bleed some out, and 24 hours later there are no issues.