Storing Matrix "Error: Bad argument type"

[MullenJohn]

Thank you for your correction.

Now I have another issue with storing a Matrix into a variable.

With the HP Prime I have created a 3x3 Matrix with the Math Template Key in Home view.
From the Entry Line, STO is press and then the variable name C1 is type.
Then the Enter key is pressed.

I receive the message "Error: Invalid input".

The matrix is
[ 1 -2 3
-1 3 -1
2 -5 5]

Please tell me what I am doing incorrectly.