Thanks for checking with us, dougs55.

I'd be glad to help you with entering bills in QuickBooks Desktop for Mac. Let's get this working.

You may want to check if your QuickBooks release version is up to date.

In-product update:

1. Go to the QuickBooks Desktop menu and select Check for QuickBooks Updates.
2. If a newer version of QuickBooks Desktop is available, click Install Update.
3. When prompted, click Install and Relaunch. When the update is complete QuickBooks Desktop for Mac will automatically open.

Once you're done updating, try to enter a bill. If the button is not working, you can try to open a sample company file and enter a bill. If you're able to create a bill using the sample company file, then let's try to verify and rebuild your data.

To Verify Data:

1. Choose Window at the top, then Close All.
2. Choose File.
3. Click on Utilities.
4. Click Verify Data.

To Rebuild Data:

1. Choose File.
2. Click on Utilities.
3. Rebuild Data.
4. You will receive a warning message to backup your company file, press OK.
5. Click OK when you get the message "Rebuild has completed".

If the problem persists,  you can uninstall and reinstall the program to fix the issue.

Let me show you how:

1. Close the program.
2. Go to the Finder menu and click Go.
3. Select Applications.
4. Click the QuickBooks icon and drag it to the Trash.
5. Download your QuickBooks Desktop for Mac version.
6. Close all running applications.
7. Insert the QuickBooks CD or double-click the downloaded installer. 
8. Drag the QuickBooks icon to the Applications folder. 
9. Open the application by double-clicking the QuickBooks icon.

These articles are a good reference:

• Reinstall QuickBooks for Mac using clean install.
• Install and set up QuickBooks Mac Desktop.

Please get back to me if you continue to get the same results so I can look further into this. Have a good one.