Can undying retrigger a second time if its +1/+1 is cancelled out by non-lethal infect damage?
Yes, if the Young Wolf loses its +1/+1 counter and later dies, its undying ability will trigger and it will return to the battlefield again.
The Undying ability is defined in rule 107.92a:

Undying is a triggered ability. “Undying” means “When this permanent is put into a graveyard from the battlefield, if it had no +1/+1 counters on it, return it to the battlefield under its owner’s control with a +1/+1 counter on it.”

It checks whether the creature had +1/+1 counters at the time that it died. It doesn't matter if the creature previously had any +1/+1 counters.
For completeness, the -1/-1 counters added by the Glistener Elf because of its Infect ability do remove the +1/+1 counter on Young Wolf, as mentioned in the question. This is specified in rule 122.3:

If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it as a state-based action, where N is the smaller of the number of +1/+1 and -1/-1 counters on it. See rule 704.