When you reinstalled you did check the LocalDB install option? Did you refresh the Databases tab in SSMS?
A Helpful TIP: If you delete a database you do not have to reinstall SambaPOS. When you restart SambaPOS it will just remake the database. Everything is stored in the Database. Also If you decide to install SQL Server 2014 you have more control over the database via SSMS vs what you get with LocalDB install.
If your interested here is the link to my tutorial for setting up SQL Server Express 2014: