When saving Group with Mailchimp settings - nothing happens

Question

I have weird issue with Civi Mailchimp extension. By looking at instructions after setting up API key, I need to update Civi Group which to be synced to Mailchimp. However, when saving group after change it doesn't affect at all and no error message. Changes to Group:

Save Success message:

And when visit back to Group again:

Another issue is with Interest Sync: I can select List and Groups from the drop down, but hit error message.

But after save:

Any one have idea around these issue? Thanks,