When you add it you are required to select to change the settings on the UI to tell it 11*17 is now in the tray, if you don't and specify to print 11*17 it will assume there is no paper of that size and fault the job.
If you have done that step and it tries to pick up the paper and jams there is a sensor issue or the stock weight/type is wrong too.
My 7100n can pick up and print from tray 1 on 81/2 x 11
But when I add 11 x 17 paper to tray 1 the printer will not pick it up
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