Main Story Quest not completing - The Aery

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Date & Time: 05-09-2020 & 06-09-2020 - 15:00 and 19:00
Frequency:
World name: Cerberus
Character name: Dragon Bish
Retainer name:
NPC name: Quest Giver - Es
Monster name: Nidhogg
Class/Level: Level 58 Black Mage
Party or solo: Joined dungeon first as solo then as a party to see if that would help
In-game time: 15:00 and 19:00
Area and coordinates: The Aery Dungeon, Nidhogg's platform
Housing: N/A
Steps:
1. Joined dungeon on 05-09-2020 in the evening, unsure of time joined the dungeon completed start to finish and at the end whilst exiting the dungeon I got the error 90002 and kept disconnecting
2. I fixed the disconnecting issue by following forum posts.
3. Reconnected and quest was not complete.
4. Redid the quest on 06-09-2020 solo at 15:00, quest still did not complete.
5. Repeated this step at 19:00 on 06-09-2020 with a party and the quest did not complete.
6. Tried to contact a GM but was told to submit a post such as this.

Connection Specs
- Type of internet connection/provider: Ethernet cable - Plusnet (UK)
- Modem maker/model number: Unsure

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If anyone has any suggestions that I can do to fix this issue that would be greatly appreciated, I just would really like to continue doing the main story quest as this is the most enjoyable part of the game for me.

Just FYI I cannot abandon the quest there is not option for me to do this.

Thanks in advance :o