I had this problem and i searched a lot for it and i didn’t get a solution apparently i solved it myself the problem is your reigon most of the times the code that you redeem is US so u need to use a vpn so close the app turn on vpn ( i use super unlimited proxy its for ios and i think for android to . Other vpns does work 
) connect to any state in the us and when u r connected open meta horizon ( the app not the website ) and try redeeming the code 70% it works if not try a different vpn if a different vpn don’t try with a different phone i hope that helps you if not check the expiration time and check the code you might have put it wrong 
Thank you stranger. You just help me fix this annoying problem. This method works on their website redeem page too.