The problem seems to be solved in the latest beta.
Get that one or wait till the final release.
OK, can you clarify this for me? First, I didn't know there was a premium version of Avast Mobile Security. I have the Pro version and that doesn't have any indication that there is a way to upgrade it to a paid version. I DO have Avast Premiere, a paid version, on my desktop, and have the AMS connected to that account. Edit: Ah, the pro version, IS the premium version. OK, I do have the paid version.
I am having the same issue as the OP on a Samsung Galaxy S8. I loaded AMS on it, connected it to my account it says anti-theft has not been enabled on my phone. When I tried to enable it from the website, the error message comes up that it could not connect to my phone. When I try to enable it on the phone itself, I am unable to set up the 'connection to Avast Account' because every time I put in my correct email address to 'Set up Web control', I get the error message that my 'Authorization failed. Sorry'. I've also called support and their only suggestion was to uninstall and reinstall - which I did - still doesn't work.
It is the correct password; I changed it just now and it works perfectly when I log into my online account from the pc - it is just the anti-theft that won't take my login.
Lastly, you say that the problem is solved in the latest beta - but I don't see a beta for Anti-theft. Is it bundled into the AMS beta?
Thank you for your patience and I hope you can help me out.