Any reason why its showing 0 available but add seems to be live?

It will available soon ,it’s in reserved status

It is because Amazon is sending your inventory to different places. It will show available as warehouse receives your units.

It is just being checked in. Not an issue. Open your inventory management dashboard from seller central and there you can see the inventory status. It is either inbound or reserved. Let it take its time.

Im getting this, does this mean I cannot sell until at least 3rd October?

No, it simply means that Amazon will take some time to fully process your FBA inventory and meanwhile the listings will be already available for purchase by buyers, albeit they won’t be shipped before Amazon completes the process, which is estimated to be done by 3rd October.