First, we recommend you to reconfigure your TV source one more time and make sure to use the right Zip Code for your Slingbox location. If the information does not match, we encourage you to check the www.zap2it.com website in order to verify the available cable service providers.
Now, if you are getting less channels than you usually get, this might be related to any kind of encryption. We encourage you to check the following link. You will get some steps to follow.
I'm having the exact same problem... using a Slingbox HD Pro 300. The HD Pro is connected directly to the cable coming into the house. The cable system recently converted to an all-digital format that required me to rescan my TV. When I tried to do the channel scan on the HD Pro, even though I know that I entered the correct zip code, the database of cable providers was woefully outdated. When I went to the zap2it.com website, it properly listed the cable system available in our area. I also know some of the higher-ups at the cable company, and they told me that they have sent updated information to the channel guide providers, so I know that the information on zap2it.com is up to date. However, the HD Pro is showing me information that is at least 5 years old!
Is there any way to do a manual channel scan on the HD Pro, like the manual scan I can do on my TV? Or, how about forcing an update of the cable providers in Slingbox's database?