According to the boiler manual
E37 Water pressure error - You must top up the water pressure for your system
When opening the fill loop valve to add water pressure, water flows out the exhaust pipe.
The boiler menu isn't interactive. Nothing happens when clicking the buttons, so I can't check the pressure via the display as suggested in several online videos.
We've contacted a boiler technician but we'd like to further troubleshoot until they arrive.
Attached images for visual reference: