Warm greetings, SHREALTY. I'm here to ensure you save your journal entry successfully.

Before anything else, please know that when adding accounts receivable for any line in a journal entry, you must specify a customer. You'll need to choose a vendor if it's an accounts payable.

When you encounter a prompt message asking you to select a customer, it won't highlight the specific entry or transaction it's related to. Therefore, we'll need to check each line manually. We can use the keyboard shortcut (CTRL+F) and enter "Accounts Receivable" in the search bar. It will locate and highlight all transactions, allowing us to select or make necessary changes.

If the issue persists after ensuring all accounts receivable line has a customer not a vendor, let's open your QuickBooks account in a private window to rule out browser-related issues. 

Here are the keyboard shortcuts:

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

If this works, return to your regular browser and clear your cache. Occasionally, the accumulated cache and cookies in the system can become outdated or corrupted, leading to unexpected behaviors. You can also switch to other installed supported browsers, which is a good alternative.

For future reference, if you want to allocate a transaction between two accounting periods or fix a debit and credit error, refer to this informative article: Reverse or delete a journal entry. 

Whenever you need help regarding journal entries in QuickBooks Online, I'm here to assist you. Kindly utilize the reply button below to enter any queries you may have.