Third Party Permission Username Paypal API Magento

I need to use paypal credentials (username, password, signature) for my magento2 store.

For credentials, I logged in to my paypal business account (provided by my client) and then navigate to Tools > All Tools > API Credentials and then click "Grant API permissions" under Pre-built payment solution. After click, it ask me for Add New Third Party Permissions link

It returns me Please enter valid API username. exception when I enter the user ID from Profile and Settings > My account settings > Manage users

Also the user ID I'm using prompts this message "For compliance reasons, we need to verify the identity of this user. Confirm identity" link.

Is it the issue because my user is not confirmed? Or should I need to add some other "Third Party Permission username" ?

With Magento 2 you won't grant 3rd party permissions, the API Username that is being asked is one provided from your Shopping Cart Provider.

You'll go into the Profile of the account and request the API Signature that you'll copy and paste into Magento 2. From your steps: Tools > All Tools > API Credentials, you'll select "Manage API credentials" under NVP/SOAP API integration (Classic)

The next page may have you pass validation via text message or phone call, once you advance to the next page you'll be asked to create the API Signature, click "Agree and Submit".

The next page will provide you the API Signature that you'll copy and paste into your Magento Store.