Sometimes, and for various reasons outside of our control, the integration connection between AssetAccountant and QuickBooks Online expires.
Although this situation is rare, yesterday you had no problems posting journals to QuickBooks Online, but trying to run the same type of journals today may fail.
Please try disconnecting and reconnecting your QuickBooks Online connection. When you do this, all of your settings and General Ledger (GL) mappings will be preserved during this process.
To do this, please visit Register Settings -> Integrations and click Disconnect.
Then click on 'Add Integration' and choose QuickBooks Online and follow the prompts to reconnect.