Hey,
after creating a ticket i got sent here to report this bug officially.
In Season 14 you said in your Blogpost:
At the start of the next Season, you’ll be rewarded with an Emblem that shows the highest rank you achieved on any weekly leaderboard in the previous season. These will be granted on first log-in to the new season
We didnt got our Rewards yet. Hope it will get fixed soon. 
Have a good evening.