When matching and reconciling the invoice you receive from LMB with the deposit in your bank account this would usually clear the invoice on your dashboard.
Some points to consider first;
Have you entered any information manually in Xero in terms of invoices?
Have you checked Awaiting Approval for anything outstanding?
Have you checked your bank for multiple deposits for the same amount?
If you've checked those things, this article will help troubleshoot as to why the invoice is still showing;
The easiest way to check for duplicate invoices within Xero is by taking a look at the settlements history. You can do so by viewing the settlement;
and select the History tab;
You can also search for duplicate invoices directly in your bookkeeping software by doing a search on the value to see if there is more than one invoice.
For Xero;
Business > Invoices
For QuickBooks;
Reports > Search for Journals in the search bar
From here you can search for the value.