As in the Circuit Image attached, I cannot access NAS from Parent Router

https://files.mycloud.com/home.php?seuuid=4105c8b4593fda5c308bc681f1d58268&name=IMG_1453

As in the circuit diagram, I cannot access NAS(2.1.1.210) which is connected to Asus Router(2.1.1.1) (DHCP mode) from CISCO(PPPOE ) (192.168.3.1) mode.

Requirement for connecting NAS from cisco is when I am not in range of ASUS(5Ghz) zone I connect to Cisco(2.4Ghz) and then the NAS becomes unreachable.

Surprising thing is I can access remotely via mycloud.com from same network diagram, but local reachability is issue.

Any guide to solve this?