Without working in QB other to print reports, the one AP Summary printed on 1/19 vs the one printed 1/21 are completely different....why?

I'm here to help you sort this out, @julie134.

You may have recurring bill transactions that were created automatically in your account. Let's view your account's audit log. This way, we'd know any changes made to your transactions list that comprises your AP Summary data.

1. Go to the Gear icon.
2. Choose the Audit Log.

From here, you'd see whether there manual or automatic changes performed in your account. You can read through this article to for more insight on how it works: The Audit Log Helps You Discover Data Errors, Boost Workflow Efficiency and More.

Also, you'd want to make sure that you use the same set of filter when viewing your AP Summary report especially the Aging method. This affects the list of information that will be displayed in your report. 

Keep us posted here if you have other questions or concerns about using QuickBooks. I'm just a few clicks away.