NETWORK DAYS and TIME calculation help

Hi

I am trying to use NETWORKDAYS to calculate whether 2 dates and times (4 cells) are more than 6 hours apart from one another but my formula shows everything as FAILED

I've attached the worksheet and below the explanation of how the formula needs to work

The SLA for urgent codes is 6HTAT (6 Hour Turn Around Time), however the shift pattern is 4.45am – 2.30am so if we receive a request between the times of 2.30 am – 4.45am (non operational hours) – then the 6H TAT should NOT start until 4.45am

Very confusing I know any help would be much appreciated

Thanks

Dan_B