I have a SharePoint list with a lookup field "Whs", and a workflow that emails when a new item is added. This list and workflow have been in place and working fine for MONTHS without any changes to them, but started failing two weeks ago with the error "The required field "Whs" data type is not supported".
I've checked other posts and verified that the lookup field does NOT have the "(link to item)" field selected in the SharePoint column - see screenshots. I changed the field to be not required, and the workflow works again, but we need the field required.
What would make the workflow suddenly stop working and error out, when it worked perfectly fine for months?