3461058 - Processing outputs of MM Purchasing documents via Manage Output items app (F2279)

You are trying to process purchasing documents' S/4hana output control (a.k.a. BRF+) related outputs via Manage Output items app (APP ID F2279)
But the sending is not possible for one or even for multiple items selected in the app.

Also the send button not does any impact on to-be-output status message via ME22n's message screen of such documents, which you tested earlier via the Fiori app too (see SAP KBA 3477238 for this symptom).

SAP S/4Hana - S/4hana output control

F2279 manage output items send senden  , KBA , MM-PUR-GF-OC , Message determination and printing , CA-GTF-OC , SAP S/4HANA output management , MM-FIO-PUR-PO-OM , Purchase Order Output Management , Problem