I have found many players (myself included) get stuck in this quest where you're meant to level your legendary weapon to level 10 before continuing. Thing is, even the weapon has reached that level, the NPCs aren't recognizing the fact.

Apparently (though not completely confirmed) being in instance/skirmishes or using experience items may lead to the quest being bugged.
Here are two screenshots showing it:

As a result, you've no access to the Legendary Weapon system, and neither Moria, which Quest Pack I recently bought at the store for a good amount of TP.
So far this issue can only be solved with the assistance of a GM; however this assistance is only restricted to VIP or subscriber members. While I understand those members should get a preferred assistance, I also believe that this situation is a result of a bug in the system and, therefore, should be able to be addressed for any player, regardless of their status.

I finally attach two links where other players have experienced the same issue with the same quest: