I asked admin of my instance few minutes ago and didn't get reply yet, but it seems your instance(mastodon.sdf.org) blocks pone.social.
EDIT: my instance isn't blocking mastodon.sdf.org
Lemmy and Mastodon are separate SDF services. OP’s instance is blocked for “anti-lgbtq, racism”.
Fans of SDF
Lemmy and Mastodon are separate SDF services. OP’s instance is blocked for “anti-lgbtq, racism”.