*60 (Call Block) is not available in all areas or for new customers. Here is what Verizon says on their website:
Note This service is no longer available to new customers. If you currently subscribe to this service, you will continue to receive the service, but you will not be permitted to re-subscribe to it if you remove it or transfer it to another customer at your current location or to a new location
This may be why you are not able to access the service. Also, what type of number are you trying to block? *60 cannot block anything but landline numbers that are in your local calling area.