I can tell why you're unable to change the detail type of the Undeposited Funds account, userp-byrd.

The Undeposited Funds Account is an internal “other current asset account” created by QuickBooks. It holds funds until you are ready to deposit them. Hence, you're unable to change the detail type.

It serves as the default 'deposit to' accounts when you receive payments and bank deposits to complete invoicing process.

Check out this link for more details: What’s the Undeposited Funds account?

Learn more about setting up accounts through this article: Add an account to your chart of accounts in QuickBooks Online.

Let me know if you need anything else with QuickBooks Online. I'm always around to help manage your bank register.