The connection to the GPM cannot be established

Faced very unpleasant problem. Just installed Grav, for a new project. When i create a new blank theme via SSH, here's what I saw when I went in the admin panel:
5
Lost all the plugins, the theme of antimatter. Right before this action, I installed dev-tools, installed and uninstalled the Gantry framework.
At the same time that the most interesting! Using file Manager I see all files including the newly created my theme!
If you need more information, no problem. Looks like a bug in the admin panel.

Open issues: https://github.com/getgrav/grav-plugin-admin/issues/976

Replied in the issue.