ROAS driving me crazy

Can anyone else help me please!

I have all clients connecting to a L2 switch, these trunk (etherchannel) into another L2 switch, which then trunk (etherchannel) into another L2 switch (core) and these have a single trunk into the gateway switch.

The gateway switch has a trunk to the gateway router, the gateway router has a standard port configured, it has a sub-interface for each VLAN along with the relevant encapsulation dot1q VLAN tag and it also has DHCP pools for each VLAN.

Clients on the user access level are able to get an IP address from the DHCP service running on the gateway router.
Clients are able to ping their gateways, they are able to ping other VLAN gateways, they are able to ping the gateway router VLAN1 address, however they are unable to ping ANY other VLAN1 address.

These VLAN 1 addresses are able to ping any other VLAN1 address but are unable to ping any VLAN 10 or 20 address (gateway or client). All L2 switches have a default gateway using the sub-interface for VLAN 1 on the gateway router. The ONLY VLAN1 address that can communicate anywhere is the gateway routers.

To get Router On A Stick working for VLAN one, do I need to set any specific configuration? I tried removing the ip address from my gateway routers internal interface and creating a sub-interface for a VLAN 1 address. I tried using a sub-interface for the VLAN along with the native tag which didn't work either.
Gateway router config
Current configuration : 3211 bytes
!
! Last configuration change at 21:33:19 UTC Sat May 12 2018
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname Gateway
!
boot-start-marker
boot-end-marker
!
aqm-register-fnf
!
no aaa new-model
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
no ip icmp rate-limit unreachable
!
!
ip dhcp pool DHCP_VLAN_10
 network 10.10.1.0 255.255.255.0
 default-router 10.10.1.1
 dns-server 10.10.1.1
!
ip dhcp pool DHCP_VLAN_20
 network 10.20.1.0 255.255.255.0
 dns-server 10.20.1.1
 default-router 10.20.1.1
!
no ip domain lookup
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
no cdp log mismatch duplex
!
ip tcp synwait-time 5
!
interface Ethernet0/0
 ip address 10.0.1.1 255.255.255.0
!
interface Ethernet0/0.10
 description *** Interface for VLAN 10 ***
 encapsulation dot1Q 10
 ip address 10.10.1.1 255.255.255.0
!
interface Ethernet0/0.20
 description *** Interface for VLAN 20 ***
 encapsulation dot1Q 20
 ip address 10.20.1.1 255.255.255.0
!
no ip http server
no ip http secure-server
!
control-plane
!
!
end
L2 switch A2 config
Current configuration : 2211 bytes
!
! Last configuration change at 21:47:47 UTC Sat May 12 2018
!
version 15.1
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
service compress-config
!
hostname A2
!
boot-start-marker
boot-end-marker
!
logging discriminator EXCESS severity drops 6 msg-body drops EXCESSCOLL
logging buffered 50000
logging console discriminator EXCESS
!
no aaa new-model
no ip icmp rate-limit unreachable
!
ip cef
!
no ip domain-lookup
no ipv6 cef
ipv6 multicast rpf use-bgp
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
ip tcp synwait-time 5
!
interface Port-channel1
 switchport
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface Ethernet1/0
 description *** CLIENT PC ***
 switchport access vlan 10
 switchport mode access
 duplex auto
!
interface Ethernet3/0
 description *** Etherchannel to A1 ***
 switchport trunk encapsulation dot1q
 switchport mode trunk
 duplex auto
 channel-group 1 mode active
!
interface Ethernet3/1
 description *** Etherchannel to A1 ***
 switchport trunk encapsulation dot1q
 switchport mode trunk
 duplex auto
 channel-group 1 mode active
!
interface Vlan1
 description *** Management interface ***
 ip address 10.0.1.31 255.255.255.0
!
ip default-gateway 10.0.1.1
!
no ip http server
!
control-plane
!
!
end