Goodman 3 1/2 ton unit

Question

i had a new unit installed (indoor an outdoor) and the house just wont cool off.the guy who installed it tried several times to fix the problem but had no success.he has narrowed it down to two things,1 he is not sure what size o*****e should be in the unit. and 2 he thinks the fluid levels could be off.i am just trying to get some help before i call someone else
air handler
ser.no.0710246971
model no.capf3642d6ba

cond. unit
model no.gsc130421ac
ser.no.0802183183