That link works fine. This is what I got as a response.
Congratulations! Your loyalty has earned you:
1x Turbo Shotgun
45 Stamina
If you have already collected a newsletter reward from a link that was shared with you then the one in your email will not work anymore. For example if I click on the link you posted again I now see this message which means I have already collected.
FAILMENTO!
Thank you for your loyalty, but you have already collected this reward. Check our App Page and Twitter often for more rewards.