That would indicate some problem with your network or router settings. If you're using Wi-Fi for everything some routers have a setting to isolate clients. You, of course, have to be connected to the same local network to access it as well.
The other possibility is that developer mode isn't "sticking". If you go through the procedure of enabling developer mode again does it give the option to disable it or enable it? If the latter (after you've already enabled it), then it's possible that your device has been blacklisted probably due to trying to sideload an IPTV channel/app or something else that violates Roku's ToS.
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