You're saying you have two separate Zotero accounts? You shouldn't — you should just have a single account, and you can add multiple email addresses in the account settings online.
The account you're posting from has no data in it, and looks to be the one that you've synced the desktop app with, so you should log out of this account in the desktop app from the Sync pane of the settings and set up syncing using the other account.
You should then delete this account to avoid future confusion and add the email address to the other account.
Upgrade Storage
The account you're posting from has no data in it, and looks to be the one that you've synced the desktop app with, so you should log out of this account in the desktop app from the Sync pane of the settings and set up syncing using the other account.
You should then delete this account to avoid future confusion and add the email address to the other account.