Having problems with APRS message delivery on 144.390 MHz. APRS is not a vehicle tracking system. It is a two-way tactical real-time digital communications system but I can't seem to get messages through reliably. My position beacons are working fine and show up on aprs.fi, but when I send messages to other stations they never get acknowledged. Path is set to WIDE1-1,WIDE2-1. TNC is a Kantronics KPC-3+ with standard UIDIGI firmware. Has anyone seen similar issues with message acks getting lost?

Check if your local digipeater network properly handles message traffic. Some digipeater owners may still be using UIFloodOptions=2 which falls short in placing the digipeat flag on the SSn-0 entry - this can break message routing downstream.

Are you using filtered APRS-IS feeds in your area? Many IGates now use filtered feeds that filter out message traffic unless directed to stations within a given range of that IGate. Message traffic to a visitor will not be delivered unless that person transmits a valid local position report.

Your path looks correct. Try reducing beacon interval to 5 minutes temporarily and monitor with UI-View to see actual packet flow. Dysfunctional digipeaters can buffer packets for long time before retransmitting, and broken digipeaters can mangle packet contents so duplicate detection fails.