If your static list contains contacts that do not yet have a permission, you will need to re-import the list and link it to the applicable permission.
Navigate to Lists, find your list and export it (see image).
Next, navigate to 'Import', click 'New Import' and select 'All Contacts'. Select your file and choose 'Opt-in'.
In step 6 'Processing', specify which permission you want to link to these contacts, this is an important step.
Under 'Add extra value to' select 'Permissions' and check 'Newsletter'.
Click 'Next' to import the list. These contacts now have the 'Newsletter' permission.
Navigate to Dynamic Lists and click 'New List'. Give it a title and click 'Edit'. Click + Selection and under 'Property' select the 'Newsletter' permission.
Save your list by clicking 'Save & Finish'. You can now use this list to send a new mailing.