If you're created a transfer record to SelectHR and no JSON export was generated, this is because the attachments on the application exceed the size limit when being converted to send to SelectHR.
As a workaround, you can:
Create the employee manually on SelectHR via the New employee workflow.
Reprocess the application in Access Recruit with no CV or cover letter attached.
To prevent this, you can apply a file size limit to the file upload questions on the application form. To request this, please raise a new case online and reference the title of this article.