Are you on premise or Cloud/SaaS?
If on premise then your reporting server is not configure correctly. If in the cloud please contact support and they will have the defaults provisioned.
Do you know if you have an SSRS instance for reporting setup and has the ISM reporting components been installed. There is a wizard you can run though to provision the reports. It also depends on which tenant is effected I am assuming production at this point but each landscape will require its own SSRS instance (some customers will only ever install for production).
Here is a link to the documentation for the install which may help (page 61 and 113):