Hi Ridwan, once you generate a new link from Zigi, you will be able to participate in the Trivia, this may be a system issue, you can contact MTN support for resolution.
You can contact MTN support via any of these channels
1. MyMTN App
2. Twitter: @MTN180 / @MTNNG
3. Facebook: @MTNLoaded
4. Instagram: @MTNNG
5. Live Chat: http://bit.ly/2OC5bHz
6. Email: customercareng@mtn.com
7. Call Center: 180 or +2348031000180 (if you are calling from abroad or another network)
8.WhatsApp: • 09033000001