How to bypass the co monitor on a 2018 Unique propane fridge?

You don't and if you did in some parts of the world you would be breaking the law.

The CO detector, alarm and safety cut-off are important safety features necessary on an appliance venting combustion gas into the room space where the fridge is sited. Carbon monoxide is a colourless and odourless combustion gas that can cause illness and even *****.

If the CO detector is faulty you should get it fixed. If it isn't faulty there should be no trouble if the fridge is sited in a large well-ventilated space.

If the space is too small and ventilation is a problem, the DV suffixed fridge should have been chosen (instead of your current choice of CM) so it could vent combustion gas directly through an external wall into fresh air.

Whether or not your fridge can be converted - try contacting the manufacturer or dealer.