Unity Admob Ads doesn't appear in some projects.

I know this is so similar topic to others but I need help about that and I couldn’t find any solution since 3 days. I found a guide for Unity Admob Ads and I applied it. It works on the project that I new created. But doesn’t appear on my existed project, I checked all layers,cameras etc. but couldn’t find any mistake.

I’ll attach a video here, about what I exactly did (1.30 min);

End of this video, I installed the apk to my device and ads doesn’t appear. Also I did same thing for another project and it worked.

My english is bad, sorry about that.

Is there anyone who can help me via TeamViewer ?