When changing hoses - You should use a thread sealer on the connections. They sell this stuff in the pluming section at Lowes and Home Depot. It will say on the small plastic container for GAS and list other applications as we'll.
Be careful with this stuff and don,t let any get on the inside of the connector where it would get inside of the hose.
They also sell a Teflon tape made for Gas lines. It is usually in a yellow container and also yellow in color.
Be sure to use soapy water to check for leaks
when finished. Dish washing soap works really well. If there is even the smallest of leak, you will see bubles.