I’ve new TLS certificate (letsencrypt) – works at the Firefox BUT: my mobile app (Kotlin) shows only blank page. I don’t know why. I searched at the internet but I cannot find the solution. My fix for some days: using old certificate.

What I must to do? This is my bash command for create certificate: letsencrypt certonly --force-interactive --renew-by-default --webroot --webroot-path /var/www -d $domain