Wifi extender N300 wont connect to internet. Please help !

Hi, Sorry if this has been posted before but im desparate for help.

Had a N300 wifi extender for a few years now. Was working fine. Never had any issues with it.

Last week it stopped any devices connecting to the internet on the extended network. N300 says it is connected to my wifi network, and you can connect devices to the .EXT network just fine. The lights on the unit show what they are supposed to show when devices are connected and are all solid green indicating good connection.

However, any device connected to the .EXT network has no internet access. Switch back to the main wifi network and everything connects fine and has full internet access. 

Have tried resetting the unit to factory settings and reconnecting (several times) and same outcomes, Have tried manual and WPS connections. Same issues.

Have also updated the units firmware to the latest release, same issues. Im out of my knowledge limits on these things now.

Logged in to the mywifiextnet page, and it says wifi extender is connected to my wifi network and is set up ready to go. But still no internet access. Basically makes the N300 useless. Anyone know if theres anything else i can do?

Running windows 10 on my home PC if thats any use, but PC has no wifi card so is connected via ethernet cable to router. That has internet access and is running fine. Like i said, N300 was fine until last week. As far as i know nothing has changed, nothings been moved, the unit hasnt been knocked etc. Any help will be much appreciated. Kids have to internet access in their rooms and we are on lockdown ! Thanks in advance