Salesforce - Enabling CORS
Salesfore Integrations widgets require that the Salesforce instance you are connecting to has Cross-Origin Resource Sharing (CORS) permitted for your community.
How to Enable CORS for your community in Salesforce Client Server
Step 1: Log in to Salesforce
Go to Salesforce and login using an admin account.
Step 2: Enter the setup panel
Click “Setup” at the top right corner.
Step 3: Navigate to the CORS Management area
In the left nav, go to Administration Setup->Security Controls->CORS.
Step 4: Authorise your community
Add your full community URL.
Step 5: Save
Click the save button to complete the process.