Certificate authority invalid?

Need some insight here. The new site works fine on desktop and laptop but for my tablet and phone I get "your connection is not private. NET::ERR CERT AUTHORITY INVALID" error message and they will not load the site. What in the world is that and what do I need to do? thanks in advance

I get in Firefox: www.lasvegasadvisor.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER

I get that same message on my Samsung Note 4 cell phone. Disappointing since I like to read the QoD every day at lunch at work. My phone is my only was to access the internet.

Getting it on my phone also, won't even let me get to the QOD. Has to be something with the new site, hopefully they will get the glitch fixed.