Chromecast not showing on Nokia fastmile router

[Vampyleo]

I have just changed my home internet from NBN to Optus 5G using a Nokia Fastmile 5G modem. Everything is working great so far except for all of my Google devices.

I reset all of the devices and connected them to the new network and they are connected to the internet & currently are showing the usual picture display but in the Google home App they show as offline when i try to check the settings for each device. Therefore there is no control from the App (my iPhone running the App is connected to the same SSID as the google devices) for any of my devices and I can't get my Chromecast(s) to show, Its only the Google devices (I have Google Mini's, Google Home, and Chromecasts connected all with the same issue)

I tried resetting all the devices and reconnecting on my old NBN modem and everything works perfectly so It seems to be that there is a setting and or issue with the Nokia Fastmile 5G modem that effects the Google devices?

I have never had an issue before when casting, from my iPhone nor previous home internet. I have 2 chromecast devices 1st gen & 3Rd both were working before this new router & internet. 
inhave set up both 2.4ghz & 5GHz on separate SSID etc, tried all the WAP/ ghz, options plus re-starting all devices every time I change settings. 
this issue was similar to another user but the fix for him has not solved mine. I was also hoping to get up my home mini. 

Any ideas to try would be great as it’s 2 weeks now no tv

[Llama]

Thanks for sharing. I have found that just about any config change fixes it but then it randomly just stops working again within a day or two.

[MLb]

Here's a simple, cheap solution so long as the Chromecast and the Nokia are reasonably close or both can access a LAN.   Go to Amazon and search for a Chromecast Ethernet Adapter.  They are available for prices from around $8 to around $20.  If the Chromecast and Nokia router are reasonably close you can connect the Nokia to the Ethernet adapter with a cable.  If not both need to be plugged into a LAN.  Connect the adapter to the Chromecast with the adapter's micro USB cable and the adapter to a USB power supply with it's USB cable and - like magic - it works! 

[kamalali]

Did an industrial facility reset on the Nokia switch.. Then changed the 2.4 and 5ghz WiFi to various names.. Designed all gadgets onto the equivalent (2.4ghz) network. Then processing plant reset the chromecast.. Appears to work now