I have investigated your issue a little on several devices and while your website works properly both in High data savings mode and with data savings turned off, there is an issue when data savings is set to Extreme - thus there may be an issue, too, when data savings is set to Automatic.
Regarding Extreme data savings mode: it seems that our requests are rejected by Cloudflare, whose servers your domain points to. This means there isn't much we can do on our side except contacting CloudFlare, which I am about to try.
What's interesting, the issue is gone if I manually change browser's user agent and as far as I know, Cloudflare offers configurable blocking per user agent. Most probably it is either this or Cloudflare defaults, but it's not common for us to have such issues with other Cloudflare-protected websites.
- Since I am unsure whether you've tried accessing your site using different data savings mode before, could you confirm that the two modes mentioned in the beginning (ie. High data savings and Data savings off) work for you? These can be set in Opera Mini menu.
- I would suggest you to take action, too, and ask your hosting service provider whether he uses Cloudflare to block specific User Agents, especially those including "Opera Mini" or "Presto".`