My understanding (which may be wrong) is that AutoSSL will try to obtain a free certificate for your site automatically, without any action required on your part.
However, Let's Encrypt won't issue a certificate to you while your domain remains on the Google Safe Browsing list. I guess this could be causing AutoSSL to fail.
You'll need to get your domain off that list, in any case. Sorry I don't have much advice to offer as to how you should go about that, as I've never needed to do it myself, but based on what little I've read...
...that does indeed seem to be the first step in the process. The next step is to check the security issues report to see what Google thinks the problem is, fix it, and request a review.