Unable to complete Defeat Faust (Level 50 and above)

[Emrys]

Procedures:

1. Talk to Grendel the Really Old at Ellinia: Magic Library.
2. Defeat Faust at Cursed Forest: Polluted Tree.
3. Then return and talk to Grendel the Really Old.

Unable to access the Cursed Forest: Polluted Tree
I was able to access it before to complete the other parts of the quest

.