Thank you for your input.
The Vizio does scan and does list the digital channels e.g. 3.1,5.1,12.1, 12.2 and in the hundreds etc., but when it comes to show the picture it does not decode them ever.
There is no "undue" splitters and the signal was measured to be +6 dB which is more than enough - cable company checked all out with a very impressive meter. As the result their finger pointed out to Vizio.
Vizio by the way gave me the telephone numbers to two of their authorized repair centers: one never answered the call, the second first took my name and number and a day later called me with the demand that they must diagnose the TV first; they wanted to diagnose by talking to me on the telephone and they wanted to charge $25 for that.
Now I am convinced that it was an error to buy Vizio - originally I thought it was suspicious that they never update their TV firmware - now I think it came full circle. VIZIO is crap! now you all know it too.