Add Attachment to Extended Absence Request

After our employees submit their extended absence request, they could be asked by our LOA team to provide additional documentation before approving the request. We have provided the Extended Absence Request History page for them to do this. However, when they select Employee Attachments, there is not an option to add any documentation. We have Attachments configured for employees to add and view attachments. Any suggestions of why our employees cannot add an attachment after their extended absence request has been submitted and before it's approved?