I had a similar issue on all 3 TVs until I discovered that you must first turn up the TV volume using the TV remote. Then you can use the Volume (+) and (-) buttons on the Cisco Digital Adaptor remote. By adjusting the TV volume, you can adjust the range of volume the Cisco remote can control. The directions that come with the Cisco box and the online directions have much to be desired when it comes to understanding what's what.
It appears to be set to fixed, not variable and is acting as a mute on/ off function. Check the menu
Many people want it that way so the TV can adjust tjhe volume, especially if you switch to Antenna, DVD or Internet viewing.
BTW, the 271 isn't a TA, it's a DTA, "Digital Transport Adapter" (another confusing acronym for a stripped out cable box) This is an encrypted Qam tuner that outputs ch 3/4 or hdmi It gives TWC control of your service without having to send a tech out.