Physical LAN not working over switch, but wireless LAN is

I have connected two computers over a switch. The desktop computer is running Linux Mint 17.3 and the laptop windows 7.

The laptop only has an IP6 address for the physical lan. Desktop has both IP4 and 6.

The laptop can ping the physical lan IP6 address of the desktop, but not the other way around (either IP4/6).

However both computers are also connected to a router (mobile hotspot) and have wireless IPs.

When using that IP the desktop IS able to ping the laptop (and vice versa).

All firewalls are off on both PCs and the windows PC has network discovery tued on.

My switch is a simple DLINK 8-p Nway switch. Bought maybe 7-8 years ago and has all lights on and blinking (indicating network traffic).

The windows laptop is on a separate workgroup.. is this a problem and how can I change it if it is?

How can I make the physical LAN work as well?