i install the latest version of JMS multisites over the old one, when i click Install button, it redirects to blank page. I have existing slavesites created, when i uninstall the multisites so i can reinstall the latest version, database error appear. Now, i cannot access anymore the master portal. Also when i checked on the slaves sites it redirect to installation process. How can i resolve this? Please help!

If you have a blank page, this is the symptom of a PHP fatal error somewhere and you have to look in your error log file the message to know the reason.

Concerning the DB connection error.
When you uninstall JMS, this restore the files that were backedup at the moment of the installation. This include the "configuration.php" file that was present in your master website at that moment.
If in the meantime, you have changed your DB connection (DB Name, user, password or table prefix), this may result by a DB connection error.
Check your "configuration.php" file and the DB connection parameters.

Hi Thank you for your help. I have enabled the error log and i was able to see the PHP fatal error. I just change the memory limit on php.ini then I was able to install successfully the latest version of JMS multisites.