Friendly suggestion: your links to the full pdf and the hardcover (both using the sabregamesandcards.com domain) are not https (and therefore not secure) so many people will never allow their browsers to go there ... I would suggest routing that domain through a free Cloudflare account which will give you an ssl cert and allow https (secure) access. The link to drivethrurpg.com is secure.
This is the warning many people will be seeing:
Actually, based on the specific message it looks like they may already have an ssl cert and just have it configured incorrectly.
Anyway, the domain sabregamesandcards.com is probably losing some business due to this so it is in everybody's best interest to get that taken care of.
So, yeah, speak to some techies, they'll know exactly what to do.