My content appears for half a second and then it disappears

I have a website where the pages we build using appear for half a second and then they disappear. Below is link to a sample page where this happens.

I also can’t access the pages in the app as well. I get an API Key error (see attachment). It doesn’t matter what page I try to open, I get the same error. Not sure if this one page is the root of all the problems.

Any ideas on how to fix this issue would be greatly appreciated.