Hi,
I have the same problem with a paid version of Avast Mobile Security on Android. I haven't lost my mobile phone but am trying to control it from the web interface to confirm that the functionality works.
My phone is connected to the internet, by wifi (and 4G, but wifi is used). From a PC connected to the same network I access my device on my.avast.com, then select Locate \ Track Device \ Every hour \ Save, and I get "We are unable to connect to your device".
Any idea what the problem is? I've tried many times with the same outcome, even though network connectivity is excellent on both phone and PC. Other commands I've tried don't seem to work either, but locate is the one I really need.
If the answer is that I should contact support, could you let me know how to do that, as I wasn't able to find any contact details on the site (but maybe I haven't looked in the right place).
Thanks in advance.