The email fails to be sent after an error occurs: Approved_Document_vod.Email_HTML_1_vod is empty.
This error may occur when the HTML file format is incorrect. This causes the Veeva HTML rendition to not be created on the Vault side.
Correct the HTML file and upload it to Vault again.
The user can refer to the HTML file format help page which is created by the BEE Editor in Vault.
CRM Help Documentation: Creating Approved Email Templates