TM MP7- No Semi Auto

[Maniac]

Hi guys,

I have had to strip and clean my almost brand new TM MP7 after drowning it (and nearly myself) in a huge muddy puddle at GZ, and how it's all clean, greased and oiled, i cannot get the fire selector to actually fire on semi auto. I have Safe and full auto and instead of semi it fires on full auto. Ive tries everything I can thibnk of to get it to work, but I'm stuck!
Any advice or help would be great!