I don't know what you are missing but I seem to be missing a LOT, like what are you trying to do. The entire formula seems wrong on many levels to me but hey, I've learned many a trick that originally looked wrong. That said here are some of my concerns:
"RIGHT(r5,1),$B$3:$k$12" -why is this is "" is that really the TEXT you are looking up?
MATCH(RIGHT(T5,1),$B$2:$K$2,"0") - this isn't an array for VLOOKUP to search - it is a number where RIGHT(T5,1) is found in the array $B$2:$K$2, except why is the last parameter "0" in ""?
Often one uses a INDEX( ... MATCH () ) instead of a VLOOKUP() so maybe you are getting things mixed up? Maybe consider using XLOOKUP() instead?
