I rolled back Easy Appointment Plugins from version 3.12.20 to version 3.12.16. It was working but when I rolled forward from 3.12.16 to 3.12.20 I lost connection to the database.
I have lost access to data for the following sections
1- Appointments
2- Locations
3- Services
4- Employees
5- Connections,

The data is there in the database but I cannot connect easy appointment plugin to the database. I have checked the setting sin config.php file and they are OK.