As I understand it, NJ non-resident returns are not explicitly disallowed from efiling. My W2 wages are not actually 0, however when asked how much of my income was made in NJ, TurboTax says to put zero if I am a non-resident. Doing so results in that error when attempting to efile. I would love to pay TurboTax for the convenience of efiling, but due to the way non-resident returns are implemented on this site, it seems that is not an option.
If you have New Jersey income as a nonresident you should report that amount instead of $0 unless your employer withheld NJ tax by mistake.
If you filing a New Jersey nonresident return because you are Pennsylvania resident and your employer mistakenly withheld NJ tax, you will have to file by mail because you must enclose a signed statement with your New Jersey nonresident returns indicating you are a resident of the Commonwealth of Pennsylvania.
The same procedure you apply if you were a remote worker in another state who should not have had NJ tax withheld.