@Seb.lumsden-1 You have changed you router wifi password, but not reconfigure your extender, right? Then your extender is not connecting to your router wifi, so internet is not available via extender...

@Jose_Maria I tried to find some information about your router. And I noticed that your router has band steering function. From my experience, this may cause unstable issue. Please disable that...

@O.mnd It seems that your PC failed to obtain IP address from your router via extender. So what's the model No. of your extender and hardware version? 854RE_V3 or other. Just check the label. or...

@Evie Hi There is no default routing on C7 because the WAN port is not used. Our router doesn't know how to reply this address because of lacking routing. I think you need use the WAN port so that we...

@19011980 Hi You can buy it on amazon: https://www.amazon.com/TP-Link-Wifi-AX1500-Smart-Router/dp/B07ZSDR49S/ref=sr_1_1?dchild=1&keywords=tplink+AX1500&qid=1588995191&sr=8-1

@JMcDermott Please refer to the instruction below to troubleshoot: https://www.tp-link.com/en/support/faq/794/ Hope it helps!