Ranked Decay

I had not played ranked since before the ranked season ended since I didn't want to lose Platinum. Since I haven't played ranked in a while, I started getting warnings that if I didn't play ranked, that I would experience decay in rank. After seeing this, I played three ranked games in ranked flex, but now a few days later, I'm still getting warnings about decay. I only have six days left. Am I supposed to play ranked in solo/duo queue where I have my Plat rank? Because if that's the case, that's impossible. The only way to play ranked right now is ranked flex on Summoner's Rift or Twisted Tree Line. Help?