For your new Roku, try using the hotspot on your phone, if possible, and connect to that just to get through the initial setup. Make sure the hotspot is set to use 2.4GHz and a channel from 1 to 11.
It's possible you have two bad Roku devices, but very unlikely. The new one can be returned, but it sounds like the other may be out of warranty.
Roku's servers have absolutely nothing to do with the ability of your devices to connect to your network. Saying, "I did every troubleshooting thing possible" isn't particularly helpful. If you have multiple Rokus that won't connect to your network it points to something particular to your Wi-Fi configuration even if every other device you own is connecting.
Dealing with Wi-FI problems can be difficult, especially remotely. All anyone can do is make suggestions, but you've already stated that you did "every troubleshooting thing possible", so I won't make any. What I will suggest is getting a Roku device with an Ethernet jack and use an Ethernet cable. Your Wi-Fi issues will be gone.
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