Standard Lead Source field is missing when creating a new Opportunity

Scenario: 

Standard Lead Source field is missing when user create a new Opportunity even when this displays checked under the Custom Form > Screen Fields > Main > Lead Source > Show = True. 

Still in the actual Opportunity page Lead Source is not displayed.

Recommendation:

1. Use Administrator role

2. Navigate to Setup > Company > Enabled Features > CRM tab > Basic Features
- Place a check mark at "Marketing Automation" checkbox

3. Read "TERMS OF SERVICE FOR NetSuite MASS E-MAIL MESSAGING SERVICES"

4. Click "I Agree" button

5. Click Save button

6. Create a New Opportunity
- Notice that "Lead Source" field is now displayed.

Note:
For additional information, view help article Lead Source.