Hi there, Tabatha S.
I'd like to dig a little bit deeper into the issue and help you resolve the error you're getting.
Can you provide a screenshot of the error or the exact error message? That way, I'll be able to check and see what's going on when turning on serial numbers in QuickBooks Desktop.
You can check out this article for more information on how to use serial and lot numbers to track inventory in QuickBooks Desktop: Use Serial or Lot Numbers.
I'll also be adding this article as your future reference if you want to set up your inventory: Set up Advanced Inventory.
I'd appreciate it if you could provide more details about this.
