There can be multiple things that would cause this error. First question I would ask is... Are you currently signed in to your Organization and does the user type that you are logging in with have permissions to publish to the organization?
What version of the solutions deployment tool do you have and what version of Pro are you running? The January 2019 update of the solutions deployment tool introduced support for Pro 2.3. If you're using an older version of the solutions deployment tool with Pro 2.3, this could cause issues.
Also, are you trying to deploy the solution to your Enterprise Portal or to ArcGIS Online?
What type of authentication are you using to access where you are publishing? (Built in users vs. IWA).