First, open your Gmail on the internet, the way you open it to read your emails.
On the top right hand corner you will see an icon of a circle with a letter or picture inside of it. Left click on the circle. Left click on My Account.
In the My Accounts page on the top left click on the words 'Sign-in & Security' Confirm that 2 step verificaiton is off. If it is on click on the arrow to the right of the word on and change to Off.
Second, In the same Sign-in & Security screen to the left top under the words Sign-in & Security click on the words 'Connected apps & sites'. The box to the bottom on the right 'allow less secure apps' change this to on if not already on.