Asking your aunt to use the same SSID and password on her new router as she did on her old router is the perfect way for your extender to hop back into your wifi router network. The extender knows little other than that it can connect to the wireless network without any problems.
However, there’s one tiny caveat that might muck up this operation. This pairing does not work if you have already set up your extender to connect to your router’s 2.4 GHz network, since, for whatever reason, your aunt uses only 5 GHz on her router. (Your aunt is more likely to use just 2.4GHz on her modem because you’ve previously configured the extender to connect to the router’s 5GHz network.)
If your aunt has renamed the wifi network, you can also bring up your wireless extender setup and make any adjustments that you need to make the link function again, connect to a different SSID, or toggle which wireless band your extender uses to connect to your router. I recommend that you run a web search for your extender’s model number and open its manufacturer’s manuals like you can type different things in your web browser to see the setup. If you’re using Linksys Extender Setup, the settings differ from model to model.
Take the Factory reset: factory-reset your extender if you’re a little confused with, or simply don’t want to fuss with, the main setup screen of your extender. Typically, by keeping the reset button down, you can do this, assuming it has one, for 5-10 seconds before the lights on the extender start blinking differently. However, check the unit’s manual to make sure you’re conducting this operation properly.
You should follow your provider’s original setup directions for your personal extender like if you have Netgear EX6100 setup in pending etc, which should make it easier to connect it to your aunt’s new router. For the first time, you’ve got your extender going properly.
Make sure you’ve upgraded your extender and router to their new firmware models. You should be able to check what firmware your router and extender are using within the web-based setup page of each device. You can then check the machine manufacturer’s support site to see if the new firmware it offers is what your device is running. If not, update it!