I’m sorry to hear you’re having trouble being able to launch your email campaign. I’m here to help!
There are a number of requirements to be able to use Shopify Email, and being on an active plan (i.e. one other than the Trial, Pause & Build or Dormant plans) is one of them. Were you previously on the Dormant plan? How long ago did you choose to upgrade to the Basic plan?
Since you are on the Basic plan now, the next step is to check that the Shopify Email app has been installed on your store. Please refer to the Help Doc for Setting up Shopify Email for more information and detailed instructions on this.
Once the app is properly installed, you will be able to proceed with creating an email marketing campaign. However, if you are still experiencing issues at this point, please reply back here to let me know and include a screenshot of any error notifications you are receiving. I will continue to work with you to ensure we get this sorted out!