Welcome to the QuickBooks Online community! I'll do what I can to get you back on track. Knowing more about what's happening when you're trying to save the journal entry will help to narrow down what's going on. Things such as error messages or the program freezing can give us clues resolving these kinds of issues.
One basic troubleshooting step you can try right away is clearing the browser's cache and cookies. Doing this ensures that you're working off a clean slate and there aren't any temporary files causing errors. Use Google Chrome or FireFox in particular to get the best functionality for QuickBooks Online.
If you happen to be using the QuickBooks Online desktop app for Windows or Mac, go to the Help menu at the top and then select Reset App Data to effectively do the same thing. Note that this will erase whatever data has not yet been saved, so you may need to copy and paste or write it down elsewhere so you can re-enter it after.
If you're still unable to save after that, feel free to give our phone support team a call at 1-855-253-1536. Agents are available from Monday to Friday, 9 a.m. to 8 p.m. and Saturday from 9 a.m. to 6 p.m. to troubleshoot with you. Learn other ways you can get in touch by clicking the Help button beside the gear icon in your account and then Contact Us.
Reach out again if you need anything else!
Thanks for performing the troubleshooting steps given by my colleague, CStuber.
I recommend contacting our phone support team if the same thing happens. They can help you out in saving your balanced journal entry and will further investigate issue.
Reach out to the Community if you have other question.