iI have not used the site lately, but as it is not really actively maintained to my knowledge , it might just not be up to the newer security standards.

Several other users also reported this in our Discord channel (which is way more active than here) and I myself also confirmed this and reported it to the GMR owners/developers.

As a work around for Chrome, click "Details" on the warning page, then click "visit this unsafe site", you should be directed to GMR site.

For other browsers, steps should be similar.

Looks like the issue is resolved:

https://transparencyreport.google.com/safe-browsing/search?url=multiplayerrobot.com

If there is anyone still seeing that deceptive site warning, please report here