Error: Getting 'null' from nested JSON array

Hello,

I’m getting the “value” : null when attempting to get a value from a nested JSON array:

Example:

We want to apply following condition for ‘meterreadings.intervalusage.interval.value’ field

if {“meterreadings.intervalusage.uom”} == “kWh F+R” then “60”
elsif {“meterreadings.intervalusage.uom”} == “kWh F” then “15”
else “invalid” end

Can you please suggest a way to solve this