Customer called in needing gas fireplace looked at. Customer can’t get fireplace to turn gas on. Upon arrival customer mentioned a couple of years ago. But now they can’t get any gas to come through the fireplace insert. Went down to the basement to look at the gas line did not see any accessible access to fireplace log valve. Went to look at the fire insert and discovered that there is a flexible appliance gas line hooked to it with a one-way check valve. Removed flex gas line and one-way check valve, turned gas on and now we’re getting gas flow informed customer that the one-way checkout was the reason why they were not getting any gas to the fireplace. Informed customer that the gas appliance line is not code to install inside a fireplace due to creating a fire hazard. We will need to hard pipe the fireplace insert. Customer made a mention that he installed the gas flex line a few years ago and has had no problems since then till now. Showed the customer the scorch marks on the flex