After creating your ECA, you need to update your Salesforce settings for trusted domains and use of cookies. Updating settings requires Salesforce Admin permissions.

Add a trusted domain for the web app where you are embedding your insights.

• At the top of any Salesforce page, click the setup gear icon, then click Setup.
  
• From the Setup page, enter Session in the Quick Find box, and then select Session Settings.
• Scroll down to Trusted Domains for Inline Frames and click Add Domain.
• Enter the domain. Acceptable formats are example.com, https://example.com, and *.example.com.
• Select Lighting Out for the iFrame type and save.

Generate the Access Token for Agentforce Conversation Client Web SDK