Hi i have now tv boxes and i am finding the software slow and yes i have updated to the newer version.
Are you connected via Ethernet or Wi-Fi?
It is possible that a factory reset might be required.
Am using WiFi i don't have a problem using my firestick or xbox.
Think it maybe time to ditch the now tv hardware.
If your not aware, since you have a Amazon fire stick you can download the NOW app for the device.
My gut tells me that NOW are going to phase out all of their hardware.