Recommendations for Relatively Easy WiFi Extender or Access Point

I bought a “TrendNet” extender/access point a couple of years ago that works well for about a day when I plug it in, but then it causes my main ATT router to stop working.

My main router is downstairs and is the standard ATT Uverse router

I have a hard wire Ethernet cable running from the router upstairs to the location I’d like to put another access point.

I don’t need a ton of range from the new access point but just want a stronger signal upstairs

Ideally, I’d like to set it up with the same name/pw as the uverse router so that it transitions seamlessly if possible.

Any suggestions on a product that would fit my needs? Or any ideas why the one I have doesn’t work with the Uverse router?