Note 1: The invitation button will be enabled when your first post reaches 4 days old.
Note: 2 You need to make a second post in this thread to enable the official invitation option.
Note 3: Make sure to share your account number (Only account number). Many time this help companies to find out you are genuine or not.
Note 4: Make sure to follow the suggestions correctly, when you do it correctly you will get the below message in your thread automatically.