You WILL NOT receive borders if you were banned after the 8/22/2017 cutoff date!

This is the official thread about Borders. Please upvote this so that I don't have to repeat myself 1000x over and over.

If you have received a 7+ day ban after the 8/22/2017 cutoff date, you are ineligible for ALL ranked rewards. You will not receive the newly implemented Profile Insignia and the loading screen borders. You will have the default (Red side, Blue side) unranked borders throughout the entire 2018 season.

Official Source:

https://support.riotgames.com/hc/en-us/articles/115011781068-2017-Ranked-Rewards-Eligibility