Problem is not just paired devices, it is all devices that have lost their OS and needed complete new installs (Avast treats them as new devices). The problem is regardless of whether accessing via the App or the online website, the Settings button does not work for dead (and missing devices). Those that were never paired show as unable to access remotely, but even the others show as active but the devices in my case no longer even exist (as Windows OS had to be re-installed 3 times from scratch on three new hard drives in just three years).
It was mentioned this should be fixed in a futured release, what is the ETA?