No response from raycast

I am still new to unity so forgive me if this is a stupid question.

I am creating movement for a player class for a 2D platformer. I am now implementing jumping for the player so I am using a Raycast to detect if the player is on the ground.

My problem is that I have a bool function which creates a ray from the center of a collider on the player to just below the player and then returns true or false depending on if the ray hits an object.

I then set a bool variable called grounded to what the function returns but it does not seem to be working

Is there anything I am doing wrong?

This is the bool function

 bool isGrounded()
     {
         return Physics.Raycast(playerCollider.offset, Vector2.down, playerCollider.radius + 1);
     }

This is where I set the grounded variable

 grounded = isGrounded();

The playerCollider variable is set in the start function

 playerCollider = GetComponent<CircleCollider2D>();