(SUCCESS!!)
Same issue, assuming the Roku Streambar's in the house updated over night, but I have Pihole setup for my local DNS. I had blocked several connections from Roku for privacy reasons:
cloudservices.roku.com
image.roku.com
rsp.web.roku.com
api.rpay.roku.com
channels.roku.com
Once I removed the block, the setup proceeded without issue.
If tech support is asking you to hotspot from another device, it means your Roku device would get another set of IP's assigned from your hotspot device, effectively bypassing the DNS on the primary network having issues (if unchanged, this is your ISP provided DNS), allowing the Roku to successfully connect to the servers for updates/app repositories for the download.
What you can also do if you do not own or manage your DNS, try setting the DNS on the Roku to other open DNS addresses to see if the connection succeeds:
8.8.8.8 - Google | DNS Address
8.8.4.4 - Google | DNS Address
1.1.1.1 - Cloudflare | DNS Address
208.67.222.222 - OpenDNS | DNS Address
76.76.19.19 - Alternate | DNS Address
4.2.2.2 Level 3 Communications DNS | DNS Address
I was not seeing the ability to set a static address for this Roku Streambar directly from the Roku settings
(if you are a Roku employee, please add this feature ASAP, I can imagine it would help immensely with your troubleshooting for customers) but if you have access to your firewall, you can modify the DHCP settings to change the DNS address DHCP will provide your device. (DHCP is what gives your device an IP address after connecting to the wireless, or plugging in a network cable)
If you can successfully set a DHCP reservation specifically for your device (using the MAC address printed on the back/bottom of the device) then you can tell the firewall to issue a specific IP address with the corrected DNS set, or if you want to just change the DNS address for all devices using DHCP, that might be easier (No MAC address necessary for this change)
I'm not a Roku technician, but I can help if anyone is having further issues.
Hopefully everyone on here eventually got their device working, but if not please send me a message on here or reply to this post and I'll see what I can do.
Thanks,
citizen3