The Roku tech support suggested these change and told Optimum the same thing:
⦁ Try to change the wireless channel as 1 or 6 or 11 for 2.4 GHz and as 161 for 5.0 GHz (Need to contact ISPS)
⦁ DHCP settings to IPV4 instead of IPV6
⦁ Disable MAC filtering
⦁ The network mode should be B/G/N
The suggestion by Roku support to use a channel 1, 6, 11 and to use wireless mode/protocol b/g/n is close to a default setting for most routers that should help most devices connect to the 2.4ghz band. The firmware of some cable ISP routers require that b/g/n be enabled for some Roku devices to be able to connect and remain connected to the network. Should be able to use g/n and n-only, but switching to b/g/n just helps rule out the above issue.
For the 5ghz band, Roku cannot see or use DFS channels (52-140), so you can use channels 36-48, or 149-161. (can also use 165, but limited to a 20mhz bandwidth/channel-width and users can be bumped from that channel if you are around military areas so best to just avoid that channel). If a router allows DFS usage, best to disable DFS in order to avoid disconnections of a Roku device.
Roku devices cannot use IPv6, so a router needs to be either configured IPv4 or IPv4/IPv6.
Regarding MAC filtering, each wireless device (and ethernet connected device) has a MAC address. MAC filtering enables and disables devices from accessing either the network or the internet (depending on setup) based on this said MAC address.
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A couple more things to look into to determine if a Roku device issue or a router (or router settings issue).
1. Similar to the MAC address filtering mentioned above, verify that you have not Paused or Blocked your Roku from your network in the Optimum mobile app. (look at connected or allowed devices settings).
2. If you have a mobile hotspot available to you, try seeing if the Roku device can connect to the hotspot. If it can connect to the hotspot, then a router setting is the likely culprit.
3. You mentioned this is a new Optimum router. Is the old Optimum router completely removed from your network (ie. unplugged from power so as not to be broadcasting).
4. Did you try the previous suggestions to remove the password completely and create an open network for troubleshooting? Or alternatively, create a simple password with no special characters.
Apparently none of the solutions are working with this router. I am going to plan B. Of all of the other streaming options available only Firestick Max is WiFi 6 compatible. Nothing against Roku. This problem is forcing me to make a change. I really love the service. Been using it for years without any problems. Hopefully Roku will update their system to work with WiFi 6 easily and correctly.
