This is a general solution for people having issues with the FROZEN PROGRESS BAR in achievements.
If you've had your progress bar for a particular achievement stuck in, say, 85% and not moving, here's what I've found out.
It is very likely that one day you started the game and started unlocking random achievements, 5 or 6 at a time. This happened to me twice, and I noticed that all achievements with progress 50% and up unlocked, and those with less than 50% went up to 75-95%.
Let's make an example for illustration purposes. We'll be using the 100 Daily Challenges achievement. Let's say that after this issue, you ended up with 85% Daily Challenges completed, when you originally had only 40%. Most people will just do 15 more and expect the achievement to unlock, but it won't. That's why many people think this is a glitch.
Even though your progress says 85%, you are still in 40%, so you will need to do 60 more to unlock the achievement, not 15.
Once your real progress catches up with your percentage, in this case 85%, you will see the bar move up to 86, 87, 88%, etc.
So this is not really an achievement glitch. Your progress bar is just showing a wrong %.
So whenever you see the progress bar stuck, just keep working on that particular achievement and you will see that eventually, when you catch up with the progression%, it will start moving as it normally would and unlock when you reach 100%.
Hope this helps clarify the confusion that dwells regarding this issue.