Cisco class-based shaping - not seeing packet matches for particular class - help greatly appreciated

I have a shaping policy applied to an ethernet interface on a Cisco ISR 4431 (IOS 15.4(3)S6 universal). This policy shapes traffic over the MPLS circuit to match varying speeds at our remote locations.

I took a pcap while troubleshooting speed issues at a particular site and found the retransmission rate kinda high (3.6%). I checked show policy-map interface g0/0/0 output and it doesn't appear the class-map for this remote site's subnet is being matched for the traffic going to that site.

I wanted to see if anyone could look over my config to see if I'm doing something wrong.

here's the simple ACL to define traffic for the remote site:

ip access-list standard 1xT1 permit 10.172.20.0 0.255.255.255 

the corresponding class-map:

class-map match-any 1xT1 match access-group name 1xT1 

and the policy-map itself:

policy-map SHAPING class 1xT1 shape average 1466800 class class-default 

this is applied to gi0/0/0 with service-policy output SHAPING

I've omitted the class-maps and sections of the policy-map that don't apply to this particular site. there's nothing different about them other than the shape average rate.

I've confirmed the subnet in the ACL is accurate and traffic is definitely being passed that should match this class, but the show policy-map int g0/0/0 output class 1xT1 always returns 0 packets, 0 bytes.

my research on this issue led me to these two commands:

platform qos match-statistics per-filter platform qos match-statistics per-ace 

I've added them and removed/applied the service-policy, but it hasn't made a difference. I'm not seeing matches when I issue show access-list 1xT1 either.

any advice is appreciated. thanks!