Hi mumtaj,
Thank you so much for your post and welcome to the Community Forum!
My apologies for the late response. If you've already used the reference number, encountering this issue is common. Try editing the reference number in the transaction you're allocating to a higher one. After saving and matching that transaction, you should regain the ability to allocate the remaining transactions as usual. You can verify reference numbers in Banking >> Transaction History.
Additionally, ensure you're not in review mode; it's indicated in the top left of the screen. If you find yourself in review mode, simply click "Exit Review" and proceed to allocate your transactions.
Let me know if these steps don't resolve the issue, and we'll explore further troubleshooting options.
Please do let me know how you go on this.
Regards,
Earl