Issues with Broadband and IP Addresses

Right, I have a Ethernet Cable running from the Sky Hub which is on the bottom floor at the front of the house, up to my bedroom which is a back bedroom, that then goes into an Ethernet ‘adapter’, I then have 1 coming from that into my iMac, and another coming out into my PS4, that has all been fine.
I have another back bedroom which is smaller but that bedroom has never got a good Wifi connection, I don’t live in a mansion, it’s a 3 bedroom (converted into 4) semi-detached house in the UK, so the distance from the front to the back of the house is not that big…. but that bedroom has always had an issue getting a connection, so I bought a Wifi Booster, which I plugged it on the stair landing, this is pretty much in the middle of the back bedroom and Sky Hub…. it has helped with getting a signal in the back bedroom but lately it hasn’t been 100%….
So, I noticed on the Wifi Booster it has an Ethernet port, so I took it into my bedroom and connected an Ethernet Cable from my ‘adapter’ into the Booster, the Booster then has been in my bedroom since… and the Laptop in the back bedroom seems to be really good now…. BUT, on my iMac, which is connected via Ethernet and Wifi, I keep getting boxes popping up now (images below)

I tried to do certain things like creating a new Location and some other things I looked up, and I thought it worked, but I just got another pop up again…..
i’ve never had this happen before, it’s only since moving the Wifi Booster into my bedroom and having it plugged into the Ethernet ‘adapter’,
i’ve now unplugged the Booster from the Ethernet and no boxes have popped up yet but i’ll restart my iMac after posting this to check if the pop up comes up again on the start up (like it did earlier today)
But why would this be coming up? is it because of the Booster being plugged into the Ethernet? as I thought having the Booster plugged in directly would help maybe give a better connection for that back bedroom?
but again, for some reason it’s messing with my iMac and messing with the Internet on the iMac to the point where I couldn’t even get Facebook to load up.
Answer #1
I think that your booster is using the same IP address as your computer, this can be fixed from your router’s configuration page : 192.168.1.1 (192.168.0.1)