A cache issue might be causing this unusual behavior. Let's try to do troubleshooting steps to fix this.
1. Use private browsing window and press the corresponding keyboard shortcut:
2. Clear the browser’s cache to remove or delete the saved activities.
If you have questions you can comment below or post again. Have a good one!
Generally you do not ever want to post to that account. You should be posting to the appropriate expense account.
That account exists because QBs will allow you to turn off the Require Accounts Preference setting (not recommended). If you do that, then QBs will automatically use the Uncategorized Expense account.
Why were you trying to use this account? Maybe we can give you a better option.