You'll need to be a little more specific on remote model number... is it a 6.3 (look at the back towards the top)?
Try removing batteries, wait a little while (minute or two), and then put them back in.
Sometimes, after changing batteries, the remote requires reprogramming... that happened to me recently (good enough reason to write your remote codes in the Dish manual).
Fresh batteries... no mix and match... would highly recommend rechargeable Eneloop from Sanyo, sold at Costco for about $25, as they have 1000+ cycle lifespan before they begin to degrade.
Comes with 8 AA and 4 AAA + adaptors for both 'C' and 'D' shells and charger.
Great on the pocket book and the environment. Picked up two sets so I could have enough in rotation = 16 AA and 8 AAA...
Haven't purchased batteries for about 8 or 9 months... doubt I will for many years to come...