Several of your documents have an expiry date — for example, your VSC and your training certificates. If one expires, you may not be able to book shifts until it's replaced.
The app tracks your expiry dates and warns you before anything lapses — you'll get reminders roughly a month, a week and a day beforehand. When you get one, open Profile, then Documents and upload the new version. The new document simply takes the place of the old one.
Renewing early is always easier than being caught out — a lapsed document can stop you working at short notice. If you're waiting on a renewal and it's close to expiring