Hi there, Bindya CPA.
Thank you for posting here in the QuickBooks Community.
If you don't see your P.O listed on the right when you try to link to a bill, this issue is under investigation. We've notified our engineers about this and they're working for the nearest solution.
In the meantime, I suggest contacting our Support Team to add you to the list affected users.
Here's how to contact our Customer Support Team:
1. Open your QuickBooks Account.
2. At the top right, click the Help icon.
3. Click Contact Us.
4. Under What can we help you with?, enter any concerns.
5. Click Let's Talk.
6. You'll be routed into the Choose a way to connect with us page.
7. Select how you want to contact them and fill in the information.
I also recommend to create a new P.O and new Bill as workaround.
Please check these articles on how to enter PO/Bill and additional information about these two types of transactions:
I'll be glad to help you if you have any other questions. Have a good day!
