E1 is burner ignite failure. This can happen if the propane pressure is too low or if the water pressure/flow is too low.
OEM recommends opening propane and using the the furthest appliance from the tank to ensure all lines are full before using the WH.
I can't recall the exact pressure or flow for water, but if you google the error code you'll get some info on it.
Also, it's far better to not use cold water, but to adjust the temp to what you want for cleaning/shower instead, then run only hot water to ensure the proper flow.
Happened to me on our second trip. Hope this helps!