wi-fi and range extender - no internet
I switched from TW plan to Spectrum plan and Spectrum switched my hardware (modem and router both). Now even my 2gh wi-fi will not reach my patio. I now have a new Technicolor modem ( DPC3216) and a new Spectrum router which broadcasts in 2.4 and 5ghz wi-fi. Problem is, the wi-fi signals from this new router do not broadcast as far as my old TW equipment, and I can't connect with my android (2.4) and iPhone7 (5ghz) telephones from my patio at the far end of the house. My wife bought us a Netgear Range Extender AC1200 EX6120 and I cannot get it to work. Both phones connect to the new networks (2.4 & 5ghz) quickly, but neither phone will connect to internet. We can connect to the old network names OK and do get internet (but not out on patio). I called Netgear support and over 2-3 hours we tried many things including factory reset on the extender, but Netgear (and I) finally gave up trying to get internet (we couldn't even find a way to download/install current firmware) . We agreed that I should return the extender.
1. is this a common problem?
2. Should I try some other extender?
3. Does Spectrum offer an extender that would work?
4. This is an average size 1 story home install, and of course cost is a consideration. Please let me know if I should do something different - and if so, what SPECIFIC router and/or extender should I buy to work with my Spectrum modem?