Move this to Products . The specified item was not found. is for generic marketing questions. And you will be more likely to get an answer as far more people will see it
I have also noticed that tokens in MSI have a tendency to behave strangely. As a result, I tend to avoid them...
It would have worked, if you sent test email through salesforce.com. Please find below the steps to follow.
1. Make an email Publish to Marketo Sales Insight
2. Go to your lead/contact in salesforce and find Marketo sales Insight section
3. Select Sent Marketo email in the Action tab
4. Select the respective templates that you wanted to test/send, then email will appear
5. Click Sent test button in the bottom of the email section.
6. You will be receiving an email with the proper first name.
P.S: If you sent test / sample email from Marketo, then token will not work. Please follow the steps as i mentioned above and test.
Hope this will help you.
Note that tokens do not work within the Gmail Plugin and will not be pulled, they only work when sent from SFDC. Be careful which tokens you use as defaults can have issues specially is lead/account owners differ or so.
Also note if you edit the email in the Gmail Plugin you break the template tracking of said email.