I'm relatively new to XMR, but am running a local node synced to the GUI (v0.12.3.0 with QT v5.7.0 on Mac). I successfully transferred coins into my primary address. I then noticed I could 'create new address,' which generated an 8xxx.... address. I then sent a txn from my primary address to this new one, however did not arrive.
The good news is that I ran the 'check transmission' using the Settings, and the transacted amount does 'prove' successfully, so I trust that this is only an issue with my GUI.
I followed the steps in this link: I am missing (not seeing) a transaction to (in) the GUI (zero balance)
Still not seeing the sub address txn. Other ideas to find txns to sub addresses?
UPDATE: The original txn was for 0.4 XMR from the primary to the sub-address. That did appear in my 'History' list as sent txn. Now, that history list shows an amount of '0' sent for that txn, and the total balance is correct as though nothing was sent. Could the inbound have somehow netted out rather than being displayed as a separate 'inbound txn?' Of note, the Payment Proof Check correctly shows an outbound amount of 0.4.