I have 2 WFs in live and I moved (via bundle) them to Sandbox. I've compared the two but the SB one just doesn't function. Basically, a button click on a case record allows you to create a PO. When the PO loads I sent a few fields. However, the subsidiary doesn't load, so I have a 2nd WF, which basically reloads the customer, and this workaround work perfectly fine in live but not SB. Any tips for solving this issue?

When was the last time you refreshed your sandbox? Are your customers and subsidiaries the same in sandbox and prod?

Refresh was done very recently, like a week ago. All the customers/vendors are in both accounts.