The Plains of Nasam bugged?

I got this quest in the Coast of Echoes, Borean Tundra. The problem comes when each time i try to hop into the tank it just disappear and so can't do the quest. What is strange is that some people is able to get into the tanks and some other people can't. The worst part is that if you don't do that quest you can't pick up the Hellscream's Champion quest, which some free exp and a really nice weapon. Do anyone knows how to make it work?

Well if other people are able to complete it so should you.
Try abandoning and re-accepting it.

I did it but i didn't solve nothing. The problem is that some ppl can and some other can't. Its a nonsense bug

I saw it reported on the bug tracker and it's marked as fixed, that's weird indeed.
Maybe make a ticket in-game and a GM will assist you.