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Navien tankless heater stopped heating water after electrical outage

last month

We have had a new tankless in operation for about 9 months now. When the contractor set it up, it was working fine. But then we had an electrical outage and I suppose the heater settings reset. Ever since then we have had trouble getting hot water.

When we turn on the faucet or shower head to hot setting, the tankless shows a 0.5-0.8 gpm flow rate as status. At this rate the heater does not begin to heat at peak capacity (I’d expect it because the heater needs to provide hot water really fast). We receive cold water.

When we go to the heater and purge it using the purge valve, the heater kicks in action at peak rate and we begin to get hot water as expected. At this time the heater status is “post purge”. This goes on for as long as the shower or faucet is running - so at this point we can enjoy hot water.

When the faucet is off, the heater goes into “dhw -wait” mode and after extended time in standby mode, and from there again there is no hot water.

Long story short, is there any way to program the settings so that the heater will kick in full capacity from standby to active flow?

I would appreciate any pointers. Currently it seems that this is not a mechanical issue but more with settings - but sadly there is no good document available.

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