Right fool proof way to set up a front mech.
With the chain off push the mech cage by hand an make sure it clears the big ring by 2-3mm It its too low loosen the band around the seat post and move the mech. If the mech doesn’t move far enough then adjust the high limit screw until it does.
With the chain on but the cable disconnected – put the chain on the granny ring and the biggest sprocket at the rear. Adjust the low limit screw until it just rubs on the chain.
Now attach the cable and make sure it is absolutely bastard tight (grip the cable with pliers and really pull. Have you barrel adjuster (the twisty thing on the bars) in the middle of its range so you have some adjustment up and down but if you have pulled the cable tight you shouldn’t need it
This sorts out 99% of front mechs.