can you check the workspaces VPCs
route table if your using s3 gateway endpoint can you if the the gateway endpoint prefixlist is added explicitly to the workspace vpc subnets route table if it’s via traditional NAT/IG can you double triple check the route table gateway entries? If it’s s3 interface endpoints can you check if it’s appropriately tied to the workspaces vpc!
all in double down cross check on the networking(subnets,sg,nacls,firewall if any) of the workspace vpc if not also check for the user access has any Denys via endpoint or iam , or bucket policies.