Appliance won't ignite on propane — quick checklist before a service call

Saves everyone time if you check these first — half the "dead" propane appliance calls end up being one of these:

1. Is the tank actually open, and is there propane in it? (Sounds obvious, happens constantly)
2. Air in the line after a tank swap or long period unused — some appliances need a few extra ignition attempts to purge air
3. Igniter battery (many fridges/water heaters have a separate igniter battery from your house battery)
4. Low battery voltage in general — some control boards won't fire an igniter below a certain voltage threshold even if it seems "fine"
5. Thermocouple or flame sensor dirty/misaligned — common on older units, especially after storage

If you've checked all that and it's still not lighting, that's when it's worth a real diagnostic — post what you've tried and what appliance/brand and I can help narrow further.