In Delivra, you must have a Professional or Enterprise license. In Salesforce, you must have Enterprise, Unlimited, or Developer editions (it does not matter if you are on Lightning or not).
The reason for both of these thresholds is API capabilities. In the Professional license for Delivra and the Enterprise/Unlimited/Developer edition of Salesforce, API access becomes standard. Salesforce Professional editions can purchase API access.
How do I check my Salesforce Edition?
Simply open a Salesforce window and hover over that window with your mouse:
If you have already attempted to setup this integration an indication that you do not have a necessary Salesforce edition, you might see this common error: API is Not Enabled for This Organization or Partner.