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Getting no where the advertised speed on the recommended router for the plan. Need Help, on wired connection with 5e cable
14 Mbps is low for a 300 plan. Perhaps that's your portion of the throughput on a crowded network?
I'd unplug the other LAN connections, disable the wireless network and repeat the test. That way, the Motorola MG7550 would be isolated to just your connected device.
Switch off the WiFi button (WLAN) on the rear of the modem. You should notice the 2 indicators on the front turn off (2.4 GHz and 5 GHz).
You could also recycle power for a few minutes. If you do, ensure the wireless network is still off. I don't know if it'd automatically enable during a boot.