Work through these before anything more involved. If they don't resolve it, the guides below cover the specific faults, and support can take it from there.
- Check the device is online. Most problems are network problems.
- Restart the affected device, not everything at once — you want to know what fixed it.
- Restart the router if more than one device is affected.
When a device keeps dropping off
If a device connects fine and then loses the POS days later, the usual cause is your router handing out a different address after a restart. Giving the POS a fixed address on your network stops it recurring. Support can walk you through it.
When it isn't the network
A card payment the POS or kiosk can't confirm isn't a connection fault to fix by restarting — the terminal has the answer. See A card payment didn't finish.
A warning when you leave a table is worth reading rather than dismissing: one of the two means your changes are on that tablet and nowhere else. See A table's changes weren't saved.