Thank you for posting here in the Community, @dung-nguyen-hp-2.
It's my pleasure to help you successfully create an expense transaction. Let's first try some browser troubleshooting steps to isolate the issue.
Please access your QuickBooks Online account through an incognito browser. Feel free to check below for the keyboard shortcuts based on the browser you're using.
If it works, it means that you need to clear your browser's cache to offload some data from your browser. This way, your browser would get optimized and we'll be able to permanently resolve the issue.
If it doesn't work, let's try using a different browser to create an expense.
If you have other concerns, feel free to comment below, and we'll be happy to assist you. Happy Holidays!