What do I do if there is no contact from owners on the day of pickup?

Did you ask for a pickup time before the dog was dropped off? You really must do this as a regular thing in order to ensure accurate billing. You should reinforce that your charges are predicated on those and that if they are late then you will have to charge them a late fee.

Now, it isn't clear if they've gone over the 24-hour mark (past the time the dog was originally dropped off). Have they? If so, then you really need to message them that the dog should have been picked up by __ time and you will have to extend the dog's stay officially on Rover. Use whatever charge you are able (day care or another night of boarding) to ensure they've paid for the entire stay.

I allow owners to go over by a couple of hours, but any longer would incur additional charges. If you make that clear to them, it usually works miracles.

Newbie like me? I know there's a lot here, but a lot of reading on this site and the FB page will help make things MUCH easier. (speaking as a newb myself)

Things could be very, wrong with this. Worst case scenario, they abandoned the dog on you. I've read it's happened. But let's not go there yet.

Best possible: cell coverage spotty/non existent where they were can lead to no replies. I just had a client like this, she responded once out of a 4-day stay, to tell me that much. Everything was cool tho.

Also, your client may be on the plane and not checking their app this morning. They may be sleeping. Perhaps another text saying, 'Please let me know asap when you will be picking up _. You may incur an additional ($amt) fee for late pickup.

Unfortunately, you painted yourself in a corner by never giving them a pickup time. Technically they haven't a clue that they can't just pick up Fido any hour they want day or night. Chalk it up as a lesson learned.