The limit screws only provide a theoretical limit to how far the mechanism can move up and down. The move to the big ring is dependant on cable tension. If you don't have enough cable tension, then you won't make the shift, it makes zero difference to how far you've opened up the high limit screw.
So you need more cable tension (assuming the derailleur is actually positioned correctly). Release all cable tension by moving the inner paddle shifter until there are no more stops. If you have cable tension adjusters either in line on the cable or on the frame stops, screw them out a few turns. Repeat until it shifts correctly.
If you don't have any cable tensioners (why do people set bikes up like this!). You need to undo the cable clamp on the derailleur, and try to pull the cable tight enough before reclamping that you have sufficient tension. If you still can't get sufficient tension undo the low limit screw all the way first, reclamp, reset the low limit then see how you are travelling.
--brett
