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Thank you so much for suggesting the above, and I have applied the above settings. But for some reason I am still running into problems.
Here is the current setup:
My Miner Configuration on website 192.168.1.99 has the following details:
Pool 1 192.168.2.99
Pool1 worker fredtheduck (this is my username for BitMinter)
My IPV4 settings are currently set at "Obtain an IP Address Automatically".
If I set
Use the following IP address: 192.168.2.254
Subnet mask: 255.255.255.0
Default gateway: 192.168.2.1
Then I lose my connection to the Internet (which is via cable).
The setup currently is I have Ethernet cable running from Antminer to Router, and a cable running from Router to Ethernet port in Computer.
Am I missing something here? Is it because My IPV4 settings are currently set at "Obtain an IP Address Automatically" ? But if I change this, I lose my connection to the internet?
I will be up all night wanting to fix this, and any help is much appreciated

then leave the IPV4 settings on "Obtain an IP Address Automatically" as the network is working.
Go to the Network -> Diagnostics page and click on the Ping button below the box with openwrt.org in it. It should come back with the important line towards the bottom