I just reached level 20 on the soulforge and then saw this.
What does that mean? Is it just a bug?
Tried to find information about the extra Khaziel quest appearing some time ago, was that one needed to unlock levels 11 - 20 of the soulforge? In that case, it might just be the message that reappeared when they launched that.
After the last major patch ( 6.2 - Mar 8, 2022) a bug appeared where the “Upgrade Available” banner for Soulforge appears whether or not you have enough runes to upgrade.
I couldn’t really peg it down but you raise an interesting theory. As you say, it might be related to the quest they added to unlock the levels. Something in 6.2 has undone the credit we receive for beating that quest. Hopefully they will fix it in the next patch (I expect it end of April or by mid-May).