Caching Problem with Humming Bird

Hello guys,

I'm using hummingbird, but it says that mod_expires isn't enabled on my server.

Browser Caching is not working properly:

    - Your server may not have the "expires" module enabled (mod_expires for Apache, ngx_http_headers_module for NGINX)
    - Another plugin may be interfering with the configuration

If re-checking and restarting does not resolve, please check with your host or open a support ticket with us.

I connected via ssh on my root and was enabling the module (a2endmod expires), but it says, that "Module expires already enabled". I restarted the apache service, but the Plugin says, that there is still no browser caching enabled.

I think it worked when I installed the Plugin. Is there maybe a problem with the update this morning?