Why have we received only a fraction of the refunds (federal, state) to which we are entitled (case xxxxxxxxx)?

Tax Return or Stimulus payments?   If it is your tax return, the IRS will send out a letter explaining any offsets made to your return, shortly.  You will be given time to dispute the or offsets or changes when the IRS decides to restart operations, hopefully soon.

If it is your stimulus payment that was shorted, you will be able to reconcile and recoup those funds when you file your 2020 tax return.  

How much is missing?  Federal and state refunds come from different places at different times.  Did you just get one?  From who?  Were you having the fees deducted from your federal refund?  Look like you are in the LIVE help version which has a higher cost.  And there is an extra $40 service charge to have the fees deducted.