AWA-Online on "[Plugin: MailPoet Newsletters] Forbidden | You don't have permission to access / on this server."

Hi there,
i am testing your plugin, but the activation Link doesnt work.

`[activation_link]Bestätigen Sie ihre Anmeldung.[/activation_link].

http://mydomain/?wysija-page=1&controller=confirm&wysija-key=cf841f92710b56f374ceda67097391c4&action=subscribe&wysijap=subscriptions&wysiconf=WyIxIl0=

I get this link to activate my newsletter registration. but i get the Errormessage:
Forbidden | You don't have permission to access / on this server.

When i am logedin in the site the link does work, when i am logged out like all other useres who gets the link to activate the Errormessage appears.

Can you pleas help me?

Thanks a lot

https://wordpress.org/plugins/wysija-newsletters/