Are you pushing the shift lever all the way across, or just to the first click?
On my 105 double, the first click moves the derailleur a little bit and lets me trim it for those times when I need to temporarily cross chain - stops the chain rubbing on the derailleur. The second click moves the chain to the big chainring. Or, a single move of the lever can take the chaing straight to the big ring just by pushing it further across. I think this is the way all Shimano doubles work...
(the shifter is compatible with double or triple)
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