You need to put a static route in the ISP router so it knows how to reach 192.168.0.x.
The syntax can vary by router, but will look similar to the route for 192.168.1.x in the tp-link.
Network Destination: 192.168.0.0 <-- the subnet behind the tp-link router
Subnet Mask: 255.255.255.0 <-- or maybe /24
Gateway: 192.168.1.41 <-- the IP address of the tp-link
Interface: LAN <-- the tp-link router is connected to a LAN port on the ISP router
Very much appreciated!