Yes,  there is a time limit for Signup and Check-ins for Shifts on the V4S Personal application.

The default app allows you to signup for a Shift before/within 60 minutes of the Shift Start Time and can Check-in within 90 minutes after the Shift Start Time.

The time limit for Signup and Check-in on the V4S Personal application for the Shift can be changed using the V4S Mobile configuration screen from the Salesforce Admin ID.