Do you have remote access to your diskstation?
My guess is if you've lost local but still have remote access to your diskstation; you've been blocked by the DiskStation security - autoblock.
The result of failed login attempts due to a mistyped username or password. Your ipaddress will be blocked on the DiskStation and you'll get the message you discribed.Do you remember enabling autoblock enter the incorrect password in?
If you are autoblocked
There's a few things you can try (from simplest to most effort)
1. Connect to Diskstation from Mobile phone off the local network and disable autoblock - then have a crack at logging in again.
2. Go to http://www.vtunnel.com and connect to your Diskstation through there (vtunnel is a proxy website that gives you a dummy ip address and location). Disable autoblock and give it attempt to login as you normally would (locally).
3. As a last resort grab a paperclip and hold down the reset pin. It shouldn't reset your data on disk but possibly resets your system partition.
I'm a big fan of the autoblock feature, remember before re-enabling it click on blocklist and remove your IP address from the blocklist.
Report how you get on.