I want to make sure we are looking at the correct issue, so -
Is it true that you changed nothing but the cable between the time it was shifting properly and when you had a problem?
To double-check - no changes have been made to the bottom bracket or right crank?
There is no reason that the same derailleur, with the same BB spindle and crank, would suddenly not be able to reach the large chainring, even by hand, and even with the limit screws removed. Cable routing would have absolutely nothing to do with such a problem, although it would make it even harder to **** far enough with the cable attached.