The solution is:
1) download previous version of Firefox from official site (https://ftp.mozilla.org/pub/firefox/releases/)
2) set system time back to 11.01.2021 or before, now you can run Kingory in your Firefox browser.

Resently our server is suffering from anonymous DDoS attacks, our security team is working on improving system firewall. We are sorry for the troubles caused by server instability. Please report your lost to support team, we will replace them as soon as everything is fine again.

Kingory World 04 patch 1.21 is coming! (2020.07.30 16:00 Kingory time)

Features:

- Unlocking pet kirin in pet system
- Unlocking special symbols in power-up system
- Resetting limited item prize of devotion
- Resetting limited item elixir of youth
- Patch related items in rebate price
- 3nd gathering contest with different rewards
- New exchange tasks in the taskgroup "event market"
- New exchange tasks in the taskgroup "daily ticket exchange"
- Free event start box in item mall