How to reset & reinstall the plugin

hi..

I had been using AAM on a few of my website.
1st time im encounter this issue, AAM icon went miss from the right panel. So i try to reinstall but it still missing.

How do i reset it? I had install wp error fix & config-press.
Hope to hear from you soon. Great plugin.

https://wordpress.org/plugins/advanced-access-manager/