Why is a password being requested to an entry that is being reversed to a period where the books are open?

We appreciate you for reaching us here. No worries, I'll provide assistance to help you make changes to an entry in an open book in QuickBooks Online (QBO). 

You will typically prompt to enter a password when attempting to modify a closed book. Once a book is closed, any transaction occurred before that date will require a password to be accessed. In your case, I suggest checking the closing date in your close books menu and see if it is changed. Here's how: 

1. In Settings, go to Accounts and Settings.
2. Select the Advanced tab.
3. Choose Edit ✎ in the Accounting section.
4. In Close the books menu, check if the closing date was change. If yes, please change it to a future date that you want. 
5. Hit Save, then click Done on the lower right of your screen. 

However, if the closing date is not changed, I recommend accessing QBO in a private or incognito browsing mode. Sometimes, the browser's cache can become filled and cause issues when working your QBO account.

See these keyboard shortcuts to open a private window:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

For a detailed step-by-step process in clearing your cache, check out this article: Clear cache and cookies to fix issues when using QuickBooks Online.

Once done, try to make changes with an entry while the book is open and let us know once it works. 

On the other hand, I'll leave this link as your guide in editing a closed books in QBO: Edit your closed books in QuickBooks Online.

You can count me in if you need additional help managing your books in QBO. I'm always ready to assist. Have a great day!