My site has a valid certificate, but Chrome marks it as insecure.
I tried my site using Brave and Firefox, and both mark it as secure.
I also ran this online test, and everything looks fine:
I am running Version 69.0.3497.100 (Build officiel) (64 bits) on a MacBook Pro.
In some threads I read this can happen if the date and time on my computer are incorrect, but they are correct.