Its not working because, the minimum interval between two periodic work request is 15 min which is defined by MIN_PERIODIC_INTERVAL_MILLIS.
Based on the documentation:
Creates a PeriodicWorkRequest to run periodically once every interval
period. The PeriodicWorkRequest is guaranteed to run exactly one time
during this interval. The intervalMillis must be greater than or
equal to PeriodicWorkRequest.MIN_PERIODIC_INTERVAL_MILLIS. It may
run immediately, at the end of the period, or any time in between so
long as the other conditions are satisfied at the time.
I would recommend you to avoid scheduling work so frequently. This will end up in consuming more resources and eventually impacting the battery life.