I just succeeded to upgrade geeklog with core plugins.
But as for the others, when I click plugins on sideblock/tools, error is shown like this:
An error has occurred:
This is being displayed as "Root Debugging" is enabled in your Geeklog configuration.
If this is a production website you must disable this option once you have resolved any issues you are investigating.
(0) - Call to undefined function ppGetUserBlocks() @ ****/plugins/nexproject/config.php line 44
I had activated only core plugins, but the error occurred.
Should I delete all plugin folders/files other than core plugins and after that download and install plugins?
I read the backtrace message and disabled access to the plungin, then it solved.