Let's check why some of your companies are missing when opening QuickBooks Desktop (QBDT) 2019.
It's possible that some of your companies where hidden reason why they aren't showing on the list of companies. To look for your files, you can search for QBW files on your computer. If you can't find it, you can make take note of its location and open then follow these steps:
Open your QuickBooks Desktop.
Go to the File menu.
Select Open or Restore Company File.
Type the location on the top address bar.
You may also find your companies on the default location of the QBDT company files: C:\Users\Public\Public Documents\Intuit\QuickBooks\Company Files.