Ethernet Not Working in Ubuntu 18.04 on New Desktop – Troubleshooting

Assembled a developer (non gaming) desktop with following configuration:

• Processor: Intel i5 8400
• Memory: DDR4-2400 8GB (double-rank), 1.2V, CL17
• Motherboard: MSI H310M PRO-VH
• HDD: Seagate Barracuda 1TB 7200rpm SATA

Then I installed Ubuntu 18.04 from the latest downloaded ISO image, via a pendrive. After connecting the desktop via the onboard LAN interface, to my home router, the interface goes into, a log Connecting state, never manages to actually connect, and finally becomes Disconnected. This is when the Wired ethernet is configured with defaults to use DHCP. Here is what ip a shows:

xyz@shivalik:~$ ip a
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 30:9c:23:b3:cd:42 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::452c:f71e:f47d:1b54/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

If I modify the Wired Ethernet interface to use static-IP, the interface seems to come up, but not work. I am unable to reach even the home router, that is at the other end of the ethernet cable connected to the Desktop. In this case, here is what ip a shows:

xyz@shivalik:~$ ip -s a
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 30:9c:23:b3:cd:42 brd ff:ff:ff:ff:ff:ff
    inet 192.168.2.220/24 brd 192.168.2.255 scope global noprefixroute enp1s0
       valid_lft forever preferred_lft forever
    inet6 fe80::452c:f71e:f47d:1b54/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
    RX: bytes  packets  errors  dropped overrun mcast   
    0          0        0       0       0       0       
    TX: bytes  packets  errors  dropped carrier collsns 
    1624       35       0       0       0       0  

The motherboard documentation says that it has the Realtek RTL8111H Gigabit LAN controller on board. Here some of the troubleshooting information I've gathered on this host:

xyz@shivalik:~$ lspci -knn | grep Eth -A3
01:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 15)
    Subsystem: Micro-Star International Co., Ltd. [MSI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [1462:7b33]
    Kernel driver in use: r8169
    Kernel modules: r8169

and

xyz@shivalik:~$ sudo lshw -C network
  *-network                 
       description: Ethernet interface
       product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:01:00.0
       logical name: enp1s0
       version: 15
       serial: 30:9c:23:b3:cd:42
       size: 100Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168h-2_0.0.2 02/26/15 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
       resources: irq:123 ioport:3000(size=256) memory:a1104000-a1104fff memory:a1100000-a1103fff

Have replaced the LAN cables (with brand new spare ones I had), but that didn't change anything. The LAN port LEDs indicate PHY connectivity it seems, on both end and they are blinking, albeit slowly. What do I have to do to get the network working on this desktop ?