Same network, Two devices can't ping each other

We have one AT&T Router on our home network. The following devices and IPs are what I'm working with:

• Desktop PC (192.168.1.86)(Minecraft) Usage: Minecraft Server
• Laptop 1 (192.168.1.85)(SKDT) Usage: Minecraft client, Node.js Server
• Android Phone (192.168.1.83)(Android (numbers)) Usage: Ping Test app.
• Laptop 2 (unknown)(Ronan) Usage: Minecraft client
• Router (192.168.1.254)() Usage: Router
• Google (8.8.8.8)() Usage: Test WAN connectivity. Also using google search works just as well.

Laptop#2, Ronan, will connect to Minecraft from the LAN. Unfortunately, I cannot charge it at the moment, so I can't figure out what settings it has. Laptop#1, SKDT, will connect to Minecraft from the WAN, but not from the LAN. I downloaded a ping test app on my phone to test the settings.

Phone Pings:

• Minecraft: Yes.
• Google: Yes.
• SKDT: Yes.
• Router: Yes.

SKDT Pings:

• Minecraft: Request timed out. Occasionally Reply from 192.168.1.85: Destination Host Unreachable as the third out of four packets sent.
• Router: Yes.
• Google: Yes.
• Phone: Yes.

Minecraft Pings:

• Router: Yes.
• Google: Yes.
• Phone: Yes.
• SKDT: Request timed out.

Things I've heard suggested:

• Firewall: It's not the firewall. I can turn the firewall off entirely for SKDT and Minecraft and the problem persists.
• Client Isolation: It's not that... My cell phone can connect to the server. My cell phone can connect to my laptop. Unless isolation can occur between just two computers, and not for the whole LAN, this doesn't work.
• And... I'm out of ideas.

So yeah, it's just two computers that won't connect to each other, even though they will connect to the same other devices. And, I should note, laptop#2, Ronan, had the external WAN ip for our network as the IP address for the MC server. On laptop#1, SKDT, I have tried both the remote and local IP's, with and without the :25565 default MC port number, and no combinations of that work.

Our Router is through AT&T Uverse, Minecraft is on Windows7, SKDT is Windows10.

I know I'm a bit late but this was exactly the problem in my case. 2 computers (also a wired and a wireless one) could not ping each other, although they belong to the same network, while other computers could ping both of them.

Spiff's comment gave me a hint:

Does SKDT's ARP table contain the correct MAC address to IP address mapping for "Minecraft"? How about vice-versa? If the answer to one or both is "no", what happens if you enter correct static ARP mappings?

I checked the ARP table with the command arp -a on both computers, to see if the other one's IP is there and then deleted them with the command arp -d <IP>.

The problem was that the wrong MAC address was cached and the computers could no longer communicate.

After further investigation, I discovered that on the laptop I had switched from wireless to wired and that's probably where things got messed up, although the wired IP was different.

So, in your case, on Minecraft you should run arp -d <SKDT IP> and on SKDT arp -d <Minecraft IP>. Then, on their next attempt to find each other, they will re-learn each other's MAC address.