Hi Aishwarya,
Thank you for reaching out to us. Please note that this forum is for us to assist you with the code implementation of the Mobile Ads SDK using the following platforms (Android, iOS, Unity, Cocos2d-x). Since you've mentioned that you're using Buildbox, I'm afraid that we don't have any visibility on how our SDK is implemented and we can't assure you that all its features will work as expected.
In addition, you may want to test your Ad Unit Ids using our sample apps (Android, iOS, Unity). If you were able to load ads using our sample apps, then this could also be an implementation issue with BuildBox.
Having said that, I would recommend reaching out to the BuildBox team so they could assist you further with this.
Regards,
Mark Albios
Mobile Ads SDK Team