I am having the exact same issue as @Myles-Powers. My stings start with $GP instead of $GN.
$GPGLL,2816.4429,N,09206.2303,W,143550,A,D5F
$GPRMB,A,9.99,R,START,CAT_SB,2900.590,N,09034.090,W,92.30,61.4,0.0,V,D38
$GPRMB,A,9.99,R,START,CAT_SB,2900.590,N,09034.090,W,92.30,61.4,0.0,V,D38
$GPRMC,143550,A,2816.4429,N,09206.2303,W,0.1,352.7,020625,0.1,W,D11
$GPRMC,143550,A,2816.4429,N,09206.2303,W,0.1,352.7,020625,0.1,W,D11
$GPVTG,,T,352.8,M,0.1,N,0.2,K,D07
Bryan