Marketo Salesforce OAuth sync issue

Hey ​@Rishabhhariyani, 

If your Salesforce org has SSO/security policies that are preventing the Marketo Sync User from logging in with username/password through the Salesforce OAuth popup, then this may need to be checked from the Salesforce side.

I would suggest checking with your Salesforce admin to see if there are any authentication policies or profile settings assigned to the Marketo Sync User that are blocking this OAuth flow.

Also, make sure you are using the correct Marketo Sync User and try the setup from an incognito/private browser. This can help avoid accidentally authenticating with a different Salesforce user.

Marketo has a helpful step-by-step documentation that walks through the OAuth setup for Salesforce. You can follow it here: https://experienceleague.adobe.com/en/docs/marketo/using/product-docs/crm-sync/salesforce-sync/log-in-using-oauth-2-0

Also, a few prerequisites as per Marketo’s documentation:

• API access must be enabled for the Salesforce Sync User (if you are a Salesforce Professional Edition user, that access is not available by default—contact your Salesforce Account Executive).
• Marketo Sync user has to be created in Salesforce.
• For existing customers, Feature to “Enable OAuth for SFDC sync” is enabled on the customer’s subscription.
• Pop-up blockers are disabled.
• Connected App is created and the Consumer Key and Consumer Secret are available for use.