Xero runs on Amazon Web Services (AWS) which is a pretty robust solution and it's unlikely to just 'go down'.
If you have any issues, the first place to check is the service status, which should tell you if there are any platform issues.
For issues with bank feeds, you can check the 'Disruptions to bank feeds' page.
Xero Service Status: https://status.xero.com
Disruptions to bank feeds: https://central.xero.com/s/article/Disr ... bank-feeds