In fact, this problem is because
Just modify the file settings, as shown below:
QQ settings are saved in a user's username, a user's username and a document \ Tencent file \
In the QQ\Registry.db file, if there is a problem with this file, QQ settings will not be saved. The solution is also simple. Delete this file, exit QQ, restart QQ, and then reset. QQ will automatically generate a new file, and you can save the settings normally.
You can delete QQ and download QQ again.