I tried creating the new webservice api for facebook lead ads in my local sandbox marketo instance. I was successfully able to do so (I have all default settings in place in the facebook developers section). For you since it is not redirecting to the fb login while adding the webservice in marketo you need to whitelist your marketo domain in the developers facebook portal. For doing this follow these steps:
Go to https://developers.facebook.com
Login to your fb account through the upper right hand link to login
Create a new app
Under the "setting" menu in the left toolbar menu select "Basic" option
Under the field of App Domain add your marketo domain and click save changes.
Save changes if needed.
In the left hand menu, click "+ Add Product".
In the list, find "Facebook Login" and click "Set Up" for it.
Select "Web" (www) in the list of options.
Verify that your "Site URL" is correct and click "Save" then "Continue".
In the left hand menu, click "Facebook Login" then "Settings".
Check that the following settings are correct:
- Client OAuth Login: Yes
- Web OAuth Login: Yes
- Force Web OAuth Reauthentication: No
- Use Strict Mode for Redirect URIs: Yes
- Enforce HTTPS: No (if set to 'yes' without possibility to edit leave it as 'yes')
- Embedded Browser OAuth Login: Yes
- Login from devices: No
Check that the section "Deauthorize / Deauthorize Callback URL" is empty.
Click "Save Changes".
From the top bar, turn the top switch from "OFF" to "ON" to make your app live.
Confirm the choice when asked. You may have to select a category and/or answer a security check. Your app doesn't require an approval from Facebook so you don't have to go through the submission process.
In the left hand menu, click "Dashboard". Your app should be public ("This app is public and available to all users") and a green dot should be displayed.
Basically an app in facebook should get automatically created upon successful authorisation form marketo side. Here we are trying to do it manually.
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