But in my experience, even if seems to fail, packets are received by the gateway, so you should see them in the log.
Just to sort out possible reasons for not receiving downlinks. Are you using ABP or OTAA, ADR, and eventually which SF? With The Things Network, there is a downlink issue when using high SF and ABP (it depends on RX2 frequency).
Regarding confirmation, downlinks are usually limited or expensive, so it is normally better to avoid confirmation for every message.