No TCP/Internet connectivity

Instances in one of my accounts do not appear to be able to access the internet. Have run through the VPC wizard in multiple regions attaching gateways etc. as usual and while I can ping external services I'm not able to get any other traffic outbound on any instance in any region. I have run through the VPC wizard on another account using the exact same options and it works completely fine there. I have also created the same config using Terraform VPC module just in case the wizard itself was the problem but still no luck.

I can see in VPC flow logs that the pings are OK but a curl request is getting a REJECT at the last step.

Could there be any restrictions at account level?

To clarify I've checked on confirmed these are all ok and again, confirmed working in another account with exact config:

• DNS is enabled at VPC level,
• gateway etc all in right subnets,
• ACL clear,
• instances & gateway have public IPs
• security group any/any outbound,
• no iptables or anything like that,
• reachability analyser shows the instances can get back to the internet gateway no problems
• route tables configured correctly

Thanks