Contrast coding for a 2x2 ANOVA in SPSS - Lmatrix error

Hello all, I'm interested in testing my data for a particular contrast. I have two independent variables each manipulated at two levels between subjects resulting in a 2x2 design. The first independent variable (MT) is coded as either 0, 1. The second independent variable (PA) is also coded as either 0, 1. The response variable is labeled as (Seeded). I have included my data set as an attachment.

Specifically, I'm looking to test whether my data follows a 1, -3, 1, 1 trend. The experimental cell related to the 3 weighting is when MT=1 and PA=0. I am using the following Lmatrix code:

/lmatrix MT 1 -1
PA -1 1
PA*MT 1/2 -3/2 1/2 1/2

Unfortunately I am receiving the following error:

This Lmatrix is not estimable. Hypothesis tests cannot be computed.

I'm not sure what I'm missing. Any help would be greatly appreciated. Thank you!!