2001 Honda Civic Cruise Control

I will be as short and specific as possible. My cruise control would not engage when I turn it on. This recently happened when a mechanic fixed my transmission. When I complained to the mechanic that fixed my transmission, he said that he did not touch anything and what he did had nothing do do with the work he did in the transmission.
What could he possible had touched to make the cruise control stop engaging? Sometimes the cruise control would try to engage but it would not hold it and just dis-accelerate.

Thanks,

Fran