Unable to watch Reward Video with Chartboost Integration

I have used chartboost sdk for monetizing app as publisher,and was working fine but from last week I am facing issue of ASSETS_DOWNLOAD_FAILURE (Failed to download https://a2.chartboost.com/production/video_icon/c842af67839244ada54bb7ea8a80076f Error message=java.io.FileNotFoundException: https://a2.chartboost.com/production/video_icon/c842af67839244ada54bb7ea8a80076f),

Please suggest what should I do? Thank you in advance.

Its a bug from Chartboost and it is In Progress to be solved, till that you can request for ads by following steps:

1. Chartboost Dashboard-> select your app
   
2. go to APP SETTING -> Reward Video
   
3. click button Revert to Default of section Reward Currency Image (80x80px)
   
4. uncheck Show Pre-Roll Confirmation and Show Post-Roll Confirmation from Advance Setting section

After or within one hour, try to request for ads.