"0/offline" error can be caused by a non-synced node and the user tried to make a transaction if the client enables him to do so.
How much premine did your Altcoin has? And was the client that you're testing 100% synced?
i set it as 10 million for a test,
I have 3 nodes, all are with addnode= to each other, my desktop 2 wallets are with a tick (100% sync)
i'm trying to send pc A to pc B, 5 million coins but fails not once but with lots of attempt.
pc A is using windows QT
pc B is using linux QT
everything is checked, no issues. Just that my qt wallet always reject the transaction as "trusted" : false.
I have no idea why