Hi,
Most of the MUSE users face this issue when they change their primary id of BUSINESS CATALYST or Adobe ID.
Go to Adobe Business Catalyst site and click on "Get Started for free", click on "Sign In", if Signed in successfully, try to publish from MUSE again
If problem remains same , you need to contact BC Help & support , Go to Live Chat option and let them know your problem.
Hope this will resolve your issue.
Thanks
Prabhakar Kumar