TLDR: Restart the destination device. If fails restart the router too.
Request Timed Out message tells your computer waited for the acknowledgment of the ping packets sent to the destination IP for a time but received none.
Common causes for this error are either network configuration errors or firewall blocking.
Since you can ping other addresses from your computer successfully, your local computer network configuration is fine.
You can ping the localhost IP (Loopback address) successfully. It means the firewall settings on your computer are fine.
So, as Andriy Zavoloka mentioned, I too doubt the Firewall settings on the destination computer. Disable the firewall on the destination computer and try to ping it again from the first device.
Even though you have mentioned you know the destination IP address is correct, I suggest you use the network discovery feature and verify if the DHCP server of your WiFi network didn't assign a different IP address to the second computer.
Sometimes a simple reboot on the second computer can fix the problem.
If the issue persists, I suggest you power off the WiFi router (I assume you have the access) and switch it on after one minute. It will reset the routing table cache on the WiFi router.
Then check for the new IP address assigned to the second computer and Ping that address from your first computer.
I hope it will fix the problem.
My Reference