Security certificate problem with mobiles

Hello everyone, I have a problem with my website and I can not find a solution on wordpress forums that's why I'm writing here in the hope that someone knows a solution. My website https://maviedecoeliaque.fr isn't accessible since this morning from mobiles (Android for sure but Iphone seems to work). From google it's accessible to some and not for others mobiles. From the facebook application also and Instagram's too. In this mobile phones the message appears: "the security certificate presents problems". From computers everything works. I called my host who told me that he didn't find any problem on my site or on my SSL security certificate. I have not changed anything on my site since last night so I don't understand. I am sorry for writing about this problem on this forum, I know that it's maybe not a theme problem but I am lost and I don't know a lot of things about computers and websites. Sorry for my English too. Thanks for your help or to give me some leads to fix this problem. Best regards. Mathilde