Common reasons applications aren't approved:
1) You are not a US based publisher and/or your content is not US focused.
2) Your website does not have an About Us page or sufficient information on your editorial staff.
3) Your content does not provide proper author bylines and/or image credits.
4) Your website contains mostly aggregated content from other sources and you do not have enough original content.
5) Your content does not meet our Community Guidelines, which can be found here.