Hello,
I have exactly the same problem, but with Kodi 17 beta 6. (All version of kodi are affected in fact...)
From Kodi debug log I see an HTTP error 503 when accessing to :
http://mirrors.kodi.tv/addons/krypton/addons.xml.gz.md5
If I use Curl to access directly this URL from my kodi I see the problem :
Cloudfare anti DDOS protection...
<h1><span data-translate="checking_browser">Checking your browser before accessing</span> kodi.tv.</h1>
The mechanism is simple, you have a javascript code (a challenge) to resolve, after 5 seconds the challenge response is sent to Cloudfare, and if it match, you get back a cookies that will avoid future verification.
Like mp3825, I use a VPN behind my router and do not want to change that. (I trust more my box provider, than my Home Internet provider...)
Do you think we can implement this verification process inside Kodi ?
Thanks.