Are there any existing topics that have helped? Have you checked to see what user and group has permission to the uploads directory (should be web:www-data)?
https://discourse.roots.io/search?q=uploads%20permissions
https://discourse.roots.io/t/upload-directory-permissions-on-digital-ocean-deployment/6261
https://discourse.roots.io/t/deploy-failure-due-to-web-apps-uploads/15646