Work around for if you install the wrong plugin, and can't then access your admin page any longer:
This was posted on Github by a disgruntled user:
Was getting same problems as above.
Was using the plugin from moodle.. and haven't bothered to upgrade for a few
months.
Decided to pull the master from here last night and give it a go.
but it hosed something within the moodle database I think .. as validated fine
but never got past the "Moodle database upgrading" part.. had to
reboot the server as I lost the ability to use admin and also to go down to
" /moodle/my/" level..
just seemed like for some reason this path was corrupt.
Had to go into "/admin/tool/log/store" and delete the plugin to get
the system back.
Running Moodle 3.1.1 (Build: 20160711) on a AWS Bitnami server.
mysql (5.6.31)
Will have to come back to this as will test on my
development server that is running 3.2.2
I actually found that I didn't need to restart the server, I'm using Debian, but if it doesn't work without a server restart, then no problem.