Strange Kodi Un-connection

I have been sorting out a friend's raspberry pi which runs as a Kodi box.
It kept on rebooting. He was using the wrong power connector.
The old sd card had errors and I clean installed OpenELEC-RPi2.arm-8.0.4.
Whilst I was working out what was happening I had it connected via Ethernet cable to my router. It kept on powering off. I don't think the router enjoyed it.
This morning it worked fine except my router didn't connect it to the internet. It connected within Kodi. It was labelled as 'Ready' and had its own IP address and MAC address but would not make any external connections.
I used a alternative wifi. Once again I checked within the OpenElec button and it was ready. This time it connected as Kodi should.
I am a little concerned. I entered my router via 192.168.1.1 and turned off the firewall. But it still doesn't make an internet connection. Perhaps I should turn the firewall back on.
The machine was connecting when it was driven by the 0.5 amp power supply but then it kept on repeatedly shutting down.
Any thoughts what I can change on my router settings?

Best wishes,
s.

The router works for all the other devices it connects to...

 

On reflection perhaps I should find a Kodi forum. Any thoughts as to where I should head?
s.

 

Here's the official forum.
https://forum.kodi.tv/

 

I picked up a 2.5 amp power source and all is well.
s.