AWS Cognito/Amplify problem - I can log in, but a page refresh logs me out

I have one project, which I’ll call “Working”, because it works fine, and all login/etc. works fine.

I copied the “serverless.yml” file and changed everything appropriate to start a new project, which I’ll call “Puzzling”.

On the “Puzzling” project, I can log in just fine, but when I refresh the browser, I’m logged out again. So I cannot do things like (e.g.) change a user’s password.

I have all the Cognito configuration in a “config.json” file, with all the right settings.

In fact, if I copy just the “Puzzling” config.json file over to the “Working” project, then the “Working” project stops working properly! So I don’t think it’s my code.

I’ve compared the two “serverless.yml” files carefully… I don’t see anything different.

Any clues VERY MUCH appreciated… Thanks!