Lately, I have seen a monstrous amount of posts relating to the MST file problem. I, myself, have dealt with this problem many times and have found some solutions, mostly for iOS users and maybe can be applied for Androids.

First off, the reason that you might be getting this message is most likely because the files that allow you to play Brave Frontier got corrupted or the files might've been wiped.

To prevent this problem, you can do either of the following:

1: Uninstall/Do not touch any battery doctors or file cleaners. Why? Because they recognize the files for Brave Frontier as "junk" and wipe them to make more space for your phone.

2: Make more room in your phone. Why? As far as I know, iOS devices automatically cleans your phone when you reach a certain threshold of data left (ex. you only have 50 bytes left) and again, will recognize Brave Frontier's files as "junk" and quickly delete them.

3: Simply reinstall the application. Why? Because when you reinstall, the game will automatically redownload the files for you.

So, when you enter the game, you will enter the "Enter" screen as normal but when you attempt to connect and check files, you get the message "REDOWNLOAD_MST_FILES" and when you press okay, your game will crash. No worries, this is completely normal. Simply reopen/kill then reopen the app and you will enter the "Enter" screen again. Login as normal and wait until you reach the "checking files" screen. It might take a couple minutes for the message to fade away and this is perfectly normal. Once through with the screen, you will be redirected to the downloading files screen. Depending on where you are and how fast your internet is, the download may take from 5-20 minutes long. If it gets stuck on a certain percentage, just wait it out because it is perfectly normal. If it continues to stay at the percentage, simply kill and reopen the app and it should finish downloading. When the downloading is finished, congratualtions! Your game is running again! Remeber to refrain from doing the things I told you not to do. Happy questing, Summoners!