If the manual button on the set works the problem is almost certain to be with the remote---These sets do have a keyboard lockout for the controls on the front of the set but it will not affect the remote---it is there so children can be prevented from playing with front buttons.
I have fixed a lot of remotes---usually what you will find is if a single or a few buttons either do not work at all OR you have to press very hard to get them to work----something got spilled on the front of the remote--it does not take very much.
The way this works is ALL the little buttons on the front of the remote are really on mat made of latex etc---on the bottom of the mat are round black coated tabs----the mat lays flat on a circuit board and the coated tabs touch matching black points on the board.
Liquid (soda, coffee etc) gets in between the mat and the circuit board and no contact occurs.
Most of these remotes wholesale for about 40 dollars but you may find one on EBAY for less.
I have taken a lot of them apart; remove and wash the mat with soapy water and dry completely. Clean the contact points on the board with denatured alcohol and dry.
put it back together and bingo--everything works.
The remote pictured is typical of Mitsubishi sets and almost any Mitsubishi remote will confirm if this is your problem or not.
If this told you something you did not know rate this solution as very helpful as I do this here for free.
REGARDS, SD TECH