I think you’ve missed one very critical part of this conversation. RevMob changed their plugin. There is enough evidence that what used to work won’t work with the new plugin and you have to adapt to the new system. You can’t count on “Ads have shown before” because you’ve not used this version of the plugin.
The PlacementID and the bannerID are going to be the same. That isn’t the problem. Your “appId” is the same as your bannerId. These numbers should be different. The chance of them being the same is microscopically (like nearly impossible) to be the same.
In my screen shots above, my appId ends with “5c9821”. My bannerId (Default) ends with “5c9823”. Yes the numbers are close, but the numbers are unique. The AppId was created seconds before the the placementId was, so they are close in value. Please make sure you’re using the right Id values.
Rob