Actually this problem also very common, google it you can find many similar questions, also shows many solution already, here we simply show how to solve this problem:
First, make sure your router modem is capable via the Ethernet ports on the device of providing 1 Gbps network speeds. Then go to the network setting and check that you LAN port is set to auto or 1.0Gb
Above picture is Intel 82574L Gigabit Network Connection Properties, it shows in below HYSTOU mini pcs:
Model FMP04-1037U Fanless industrial PC, 2*Intel 82574L Gigabit Lan, 1*VGA+1*HDMI dual display, 4*RS232 COM, item link https://www.topminipc.com/mini-industrial-pc-c1037u
Model FMP04-i5-3317U Fanless industrial PC, 2*Intel 82574L Gigabit Lan, 1*VGA+1*HDMI dual display, 4*RS232 COM, item link https://www.topminipc.com/mini-itx-pc-i5-3317u
Model FMP04B-2955U Fanless Industrial PC, 2*Intel 82574L Gigabit Lan, 2*HDMI dual display, 6*RS232 COM, item link https://www.topminipc.com/mini-itx-pc-celeron-2955u
Model FMP04B-i3-4010U Fanless Industrial PC, 2*Intel 82574L Gigabit Lan, 2*HDMI dual display, 6*RS232 COM, item link https://www.topminipc.com/small-form-factor-pc-i3-4010u
Model FMP04B-i5-4200U Fanless Industrial PC, 2*Intel 82574L Gigabit Lan, 2*HDMI dual display, 6*RS232 COM, item link https://www.topminipc.com/fanless-indus ... c-i5-4200u
Model FMP04B-i7-5550U Fanless Industrial PC, 2*Intel 82574L Gigabit Lan, 2*HDMI dual display, 6*RS232 COM, item link https://www.topminipc.com/industrial-computers-i7-5550u
Simply, FMP04 and FMP04B series industrial mini pc using Intel 82574L gigabit lan, other mini pc using realtek gigabit lan, Realtek PCIe GBE Family Controller Properties window shows below:
