Form Workflow Plus columns need to be in Row 1 of the worksheet. The add-on looks for these column titles when updating the approval status. If, for some reason, these columns are moved to another row this error message appears when a reviewer sets a decision on a request:
“Error: Unable to parse range: Form Responses 1!:”
To fix, simply revert the Form Workflow Plus columns to Row 1. Reviewers would then be able to work on requests as normal.