Job Withheld Money From Checks And Is Refusing To Pay Them Because It's "dead Money"

I work for a large hotel chain that is managed by a smaller company. Recently we had a new computer system installed and about a week or so later it crashed leaving us unable to charge credit cards so we are left to do room charges and cash (we are a chashless property normally). Long story short there is money missing from mine and other co workers checks. This is due to a clerical error by the front desk people not manually entering the tips when the machine was down. Since the computer was down the room charges needed to be entered at the end of the night manually which they did not do. There is a whole stack of unentered checks and accounting/ the GM don't seem interested in fixing/ wanting to pay the owed money because they couldn't process the card on the room because the guest has already checked out so it is "dead money". Is this legal sorry if my wording is dumb thank you for any help!!