Custom alert not work on 8.1

[Bodye Foll]

I almost give up to set custom alert on my lumia 1020 (wp 8.1). I downloaded ringtone (mp3) from web, and i want to change default alert on windows with my custom ringtone. i have already read and watch video on youtube which tell how we can change alert for app. it's look like easy, and i can see their custom mp3 ringtone on list. but i still can't do that, it's strange... but i don't know that tutorial for 8 or 8.1.,
Whether windows 8.1 can not use custom alerts?

i have already put my mp3 to ringtone folder (transfer via windows 7 pc), and my mp3 is non DRM, it's free from protection, and i can play that ringtone on my music player on my lumia 1020, but i can't set that music file to my alert/ringtone.

can somebody help me please? i want to change my bbm,email and other app alert. of course my phone ringtone too.. default ringtone on windows is not good at all for me..

Thx

sorry for my bad english

 

[Bodye Foll]

anyone can help me please?

 

[Dhileepudu Jambula]

Thats Strange as I can see the mp3 files which I just copy or drag and drop to the ringtones folder in my HTC 8X.

I have set custom ringtones for each app.

I dont know whether its a better idea but try to keep mp3 files which are of less duration(30 sec play) and if its still not able to recognise then its the Mobile Software which isnt syncing or you need to hard reset(just assuming)...