Wired & wireless connection.

This is somehow a 2 topics thread, not necesseraly connected.

1.
One W10 Pro 22H2 with drivers/OS updated WiFi laptop with internet access.
One W10 pro 22H2 drivers/OS updated intel NIC RJ45 desktop also with internet access.

They're IP assigned by my internet box DHCP.
Both of them are private network set, same workgroup, discovery ON, files & printers shared.

The issue is that pinging and shared folder ONLY work one way : desktop => laptop is ok, laptop => desktop isn't.

Why ?



2.
Gigabit desktop network NIC beginning to fail, I've switched to a NIC with an intel 82576 - E1G42ET Chip (failing was a realteck one).

My network is :
fiber internet box => gigabit trendnet switch TEG-S380 8 <= desktop/synology NAS.

I've discovered that previous NIC was failing by the LED of the switch desktop port showing a gigabit_10/100mb/s. W10 also stamped it 10/100mb.
Pluging the new NIC, no led on the switch, no network access despite being ok in W10 devices manager.
After many tryouts and before getting back to the seller, I've plugged the desktop directly on the box... Instant access.

Why ?

I thought the issue to be on laptop side when it is in fact desktop side.

Needing to use an old canoscan and moving an also old XPMode x86 from w7 being so §%*µ$£@\{#, I've installed my old XP in vmware to find that despite being able to access the internet I just can't see the host.

I've just check, desktop is private network, printer & file sharing on, discovery on, on the same network. I've even disabled firewall without result.

What is the @+$£&!§*% going on ?
What parameter, setting is f!/§ù%^¨$£ing blinding this w10 pro from others on local network ?