Take the following steps in order as needed:

1. Click the binoculars under "Search for an Invoice by Invoice Number"
2. Remove any query set above in the field for "Search using query"
3. If only one invoice is still opening, click the options button and click the "Restore default Invoice Query" button.
4. Change the option for "If only one record is found" to "Display the record in the search results window"
5. Click Ok
6. Search for the desired Invoice through Open an Invoice