I would hazard a guess that the Softaculous upgrader is your issue since the multiple manual upgrades I performed have not had this issue.
Did you install to a different directory?
Did you check to make sure that you are running the most recent version of the LDAP plugin?
Take a look at your ost_plugin table.
What does it say the install path is? Is that the correct path?
What does it say for isphar (1 or 0?)
You can try deleting the plugin from osTicket via the UI. Then try re-adding it.
If that doesn't work you can manually remove the row from the ost_plugin table. [Back up your DB first!]
Then try re-adding it.