I have been playing Forza Street for fifteen days and the progress bar was stuck on 71% at seven days of logging in to the game until today. What I did was install the game on different iPad I have, but this method may work the same if you have a single device. The key for me to getting this to unlock was to be signed out.
The only way this can happen that I can figure out is uninstall the game so when you start the game up again, you are logged out. You play through a couple minutes of the beginning stuff and after your tutorial and first race, you will get a prompt. It will ask you to login to Xbox Live. As soon as you do this, another window comes up that says that you have progress in Forza Street on this or another device, and do you want to replace your progress on starting the game on the current device with what you have accomplished elsewhere or on the existing device before you uninstalled the game. Click "Yes" and the game will restart.
Note that Forza Street daily login rewards happen each day at a certain time. For me, it happens at 10:00 p.m. Make sure that when you boot the game up after a reinstall, that it is when you know a daily login reward is ready to claim. I waited until 12 midnight just to be sure. When I went through the above process and claimed today's reward, the achievement popped.
I tried to get the achievement by installing the game in Windows 10 and the progress I had automatically credited from my iPad play and the achievement did not pop. I am signed in to my gamertag all the time on my Windows laptop. The achievement only popped on another iOS iPad where I had to sign in from scratch.