Whirlpool side by side Gold series

Freezer is not freezing, not getting cold enough. the condenser is not clicking it is vibrating and running. the fan on outside underneath is running, the fan inside in freezer section is running, there is no build of frost. it was unplugged and completely defrosted. i re-plugged it in starting to diagnose it took back panel off in freezer, the fan runs, but the coils inside get frost on them only about two rows from bottom. the rest show no signs of frosting. i know a little, but not enough to figure it out thank you for any help.