If that is your dad's computer it is using a wireless connection.
The computer is getting its' DHCP IP address from the Router 192.168.0.1.
You blocked out the provided DHCP IP address (which is not necessary to do). However, you do want to ensure that no other devices on your home network are using that same DHCP IP address.
FYI:
https://www.lifewire.com/what-is-a-...vate IP address is,a home or business network.
You can easily search for and find similar links and explanations.
I also noted that your dad's computer is using a USB wireless dongle. Is that USB dongle plugged into the back of the computer? In any case, try using a USB cable extension to raise the USB dongle up and away from the back of the computer. Objective being to generally improve wireless reception and, more importantly, transmission via that wireless adapter. Keep a steady signal.
If the dongle feels very warm or even hot, then the dongle may be failing. Check by feel when the computer has been off for awhile. Then continually and carefully continue to check after booting up and successfully getting connected to the network. Hot will be quite apparent.
Another immediate issue is the Lease time. Change the Lease time on the router to at least 7 days (168 hours).
If your ISP does not provide IPv6 - disable IPv6.
Next: physical connectivity (line diagram, typical home network) Where ----> indicates an Ethernet connection.
ISP == Coax, DSL, fiber ==> Modem ---> [WAN Port] WR 840 Router [LAN port] ----> wired devices with one LAN port --->[LAN] WR 740 [LAN] ---> other wired devices (but there are none: no printers, NAS boxes, internet TVs, etc..
Correct?
And, as I understand there is ~~~ (wireless) ~~~> connectivity to 14 devices total.
Where does your dad's computer "fit in".
Edit and correct my line diagram as necessary.
Do both routers have the same IP address (192.168.0.1)? If not, what IP address is each router using? Which router do you expect that your dad's computer is connecting to?
Only one router (the WR 840) should be provided DHCP IP addresses to network devices. DHCP should be disabled on the 740 router.
Use the following TP Link to check your current network configuration.
https://www.tp-link.com/us/support/faq/357/