Unable to connect to sntp server from Adtran router

I'm trying to have the company's routers sync their clocks with a sntp server on the internet, but they're not getting a response (I see that by using the 'debug sntp client' command). What am I missing?

The following is the Adtran configuration (with certain portions erased):
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show running-config
Building configuration...
!
!
! ADTRAN, Inc. OS version 18.02.04.00
! Boot ROM version 13.03.00.SB
! Platform: NetVanta 3448, part number 1200821E1
! Serial number LBADTN0951AA160
!
!
!
clock timezone -5
clock no-auto-correct-DST
!
ip subnet-zero
ip classless
ip routing
ipv6 unicast-routing
!
!
ip domain-proxy
!
!
no auto-config
!

!
no ip firewall alg msn
no ip firewall alg mszone
no ip firewall alg h323
!

!
no dot11ap access-point-control
!

!
vlan 1
  name "Default"
!
vlan 2201
  name "
!
vlan 2202
  name "
!

no ethernet cfm
!
interface eth 0/1

!
interface eth 0/1.1

interface eth 0/1.2

!
interface eth 0/2

!
interface switchport 0/1
  no shutdown
!
interface switchport 0/2
  no shutdown
!
interface switchport 0/3
  no shutdown
!
interface switchport 0/4
  no shutdown
!
interface switchport 0/5
  no shutdown
!
interface switchport 0/6
  no shutdown
!
interface switchport 0/7
  no shutdown
!
interface switchport 0/8
  no shutdown
!

interface vlan 1
  ip address  10.10.10.1  255.255.255.0
  no shutdown
!

ip route 0.0.0.0 0.0.0.0 10.1.220.254

!
no tftp server
no tftp server overwrite
ip http server
ip http secure-server
no snmp agent
no ip ftp server
ip ftp server default-filesystem flash
no ip scp server
no ip sntp server
!

ip sip udp 5060
ip sip tcp 5060

!
ip sip proxy grammar contact outbound-server-reference host domain
!

!
line con 0
  login
!

!
sntp server 204.34.198.40
!

end
--------------------------------------------------