System settings - Unexpected token

When I visit system->system settings , this error appear

Unexpected token <:
Forbidden
You don't have permission to access /connectors/system/settings.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

And there are no settings set.

Please, what should I do ?

Is this a new installation? Did you unzip the installation package and upload it file-by-file? If you did, it is common to have some files either fail to upload altogether or get corrupted during the upload process. It is best to upload the zipped package and unzip it in place on your server.

For anyone who might be having a similar problem on a fresh install, it took about two days of constant uploading and new installs before it finally worked. It required a complete re-upload and re-install to make it work (I was trying to re-upload the connectors folders without success). Core was always uploaded as zip transport and unpacked during install.
I hope this helps somebody, as it seems that uploading through FTP has a high chance of corruption.