Can’t add links

When adding new links at …/wp-admin/link-add.php

I get an error message at …/wp-admin/link.php that reads:

Not Acceptable
An appropriate representation of the requested resource /wp-admin/link.php could not be found on this server.

I downloaded the link.php again from wordpress and uploaded it to the site in case the original was corrupted, but no different.

I was able to add links yesterday.

ANy ideas?

Thanks