Having an issue: I keep getting notified that Jon Snow wants to see me at castle black, but I can't accept. I either get several lines of red code, or clicking "Accept" does nothing. Anyone got a fix or workaround? Am I missing something?
I've had this a couple times. The only way I've managed to fix it is to make sure he's actually there.
When you face the whitewalkers with him, make sure he survives - as an archer, take double or triple obsidian (or fire) arrows and have him retreat immediately, kill as many as you can, then retreat and repeat until they're all down (you can probably just bail but the XP is just too good). As anything other than an Archer you'll need a Valyrian weapon. I've read that you can use Thoros of Myr's fire sword if you have him recruited, but I've not yet tried this. You can also "Change Commander" to take control of Jon directly and use his Valyrian blade, but I think that puts him at risk (not sure if he just gets knocked out or can actually die if you're controlling him directly?)
Also make sure he survives all the way back to Castle Black to turn in the quest.
Once he becomes Lord Commander, he'll need to be free (ie, not imprisoned somewhere by Wildlings) or you won't be able to pick up the quest from him. I've found he can usually manage this on his own, but it might be worth sticking around a bit, or trek around in or near the North, to make sure the coast is clear.