This is a simple clogged drain, Ron. Take the back panel off the freezer so you can see the drain trough under the evaporator coils and thaw it out. You'll need a good hair dryr or a steam gun, my weapon of choice in thawing everything these days.
Once you get the slab of ice from the trough, pour boiling (or at least very durn hot) water down the hole to complete the process. I usually add a capfull of bleach at this point to retard algae growth. Keep that temp control in the FF section to the miday point...if you turn it up too cold you'll freeze up again.