A renter is "locked out" of their account if their credit card declines. Their only option when logging in is to update their credit card information. If they update their card and the open balance clears they will no longer be "locked out".
If you want to remove the Non-Payment Lockout, please follow these instructions:
Step by Step Instructions
From the Dashboard, select Customers
Select Renters on the left menu
Choose a Renter
Select Statement from the sub menu
Click the Settings gear above the Date on the left side of the page
Select Remove Non-Payment Lockout
Non-Payment Lock Out alert is shown in red ! indicator.