For a few weeks now when trying to insert any picture or video into a Blogger article I get the above annoying prompt.
[The temporary solution was to use Firefox to create and edit Blog articles.]
But when you sign in, it does not lead anywhere ....
After a lot of research, here is the 'in retrospect' obvious answer. It is to allow 3rd party cookies from any google.com domain.
In Chrome you would do this:
Show Advanced Settings
Add the exception for anything.google.com
That is it.
Now you can again Insert Pictures and Movies without that ridiculous error!