Good day Alicia,

Have you tried removing the lookup field from the form, saving and then adding it back again?

Hi,

I have the same problem

If you define a lookup column site in the root web and use it in sub web, you can't access to the value in a workflow

I have the same error than Alicia

Regards

The problem is that the lookup value on the list has changed.  You need to recreate that at the list level first then import that back into your form and workflow.  When you changed the list location, the GUID supporting the lookup column broke creating the issue you now see.