Index Match Formula Issue - Lookup Value is a Formula

Hi,
I am having trouble with my Index Match formula. The lookup value (column C) is in the adjacent cell but it is a formula. It works on the cells that have letters in them. But, the ones with all numbers if does not. If I add a value function to the formula it works. But, only on cells with all numbers. Would like to find a way it would work with both all numbers and cells with letter number combinations. Please see my attached example.
Thanks in advance for the help.