@denserges -- which cable-modem/router do you have? Hitron? XB6? XB7? All three devices broadcast both 2.4 and 5 Ghz WiFi networks.
What is the manufacturer & model-number of your tablet?
Does your tablet support only 2.4 Ghz or both networks? To which network are you trying to connect?
If you force a connection to the 2.4 Ghz network, do you get that error-message? Same question, for the 5 Ghz network?
When you logon to your cable-modem/router, and view its "wireless" configuration, are the security-settings identical for both networks?
