I am not native English, but will try to reply.
"to may" is used for requests and offers.
In this case you say that it's going to work again, it's not a gentle request or offer.
"May you help me?"
"Yes, I may"
"After studying together, you should have learned."
(There can be other random mistakes, sorry.)
Maybe it's common practice in English to use "May" in other contexts, but this course should be easy for non-natives as well...
It doesn't have to be about requests or offers. If you say that something
should work again, you say that it is expected or logical that something will work again. If you say that something
may work again, you say that it is possible that it will work again but you are not certain.
I presume it "is allowed, or it can now, it may, work again"
I think the reason why people might be confused on this one is because according to various German-English online dictionaries, dürfen seems to usually mean "may" not "should." I think in English, "may" doesn't just mean a polite request as marziotta explained, but also means "might," and in this case the sentence seems to be saying, "It MAY work again" ie. "It might work again, but we'll have to wait and see." But yeah, I guess there's more of a clear distinction between "should" and "may" in German, but what's wrong with "sollte" here? Why dürfte and not sollte here?
Try http://www.oxforddictionaries.com/us/words/may-or-might for a discussion of may and might in English. .