This is the Happy Dungeons Management Team.

From 7:00 am on August 25 (UTC) to 2:00 am on August 28, the issues occurred with players couldn’t register their Gamertag in the happydungeons.net campaign.
We would like to sincerely apologize for any trouble this may have caused.
If you register your Gamertag during 7:00 am on August 25th to 2:00 am on August 28th, please re-register it.

We would like to thank everyone for their patience and support, and will distribute 10 Happy Jewels to every account.
https://www.happydungeons.net/pr/xbox_ps4rel_campaign_en/

Again, we would like to offer our sincerest apologies for any inconvenience caused by these issues. We look forward to seeing you exploring Happy Dungeons again soon!