Get error 403 after installation and activation

Thx for using our plugin. There is no such thing as activating the plugin. Do you mean installing and using the “Management interface”? See https://docs.fast-events.eu/en/latest/apps/admin.html#administrator-accounts

It can only be istalled by an WordPress admin account and used by an admin account. For any other regular WordPress account. Read this section https://docs.fast-events.eu/en/latest/apps/admin.html#server-accounts

If the 403 is in another part of the plugin, please specify the url and the WordPress account role (admin, regular, …) you are using and we will look into this.