From this morning's Deadline Hollywood...
The impasse in negotiations between Tribune Media and Dish Network over market rates was unable to be resolved before the expiration of the deal between the two companies, and Tribune channels have now gone dark in 33 Markets on Dish. The companies failed to reach agreement on an extension of the current deal that would continue service while a new deal is worked out.
There are more details at the link, but this is strictly a hardball negotiation.