If you’re trying to connect your Marketo Sales instance to Salesforce and you’re seeing the “We are unable to authenticate your request” error, it’s likely related to how your Salesforce instance is configured.
There are two types of errors that could be producing this failed authentication page.
You can identify which type you’re getting by checking the URL.
This error typically indicates you have a custom domain that we’re not able to route to. To resolve this error, try signing in to the Salesforce instance you want to connect to first. Then, go through the steps to connect to Salesforce.
If the instance you’re trying to connect to is a Salesforce Sandbox domain and you’re getting an error, you’ll need to go through additional steps to update your instance to be Salesforce Sandbox compatible. Learn more.
If you received the error message “We were unable to authenticate your request” with the Oauth App Blocked error type (or another type) in the URL, there might be a restriction on your access to Salesforce’s API. Check with your Salesforce Admin to make sure the things below are in place.