I follow my own Pixelfed account on Mastodon and will often boost posts. I have a pixelfed.social account though. It’s probably a federation issue on your specific Pixelfed instance. I’ve moved the Mastodon account a bunch and I’ve had problem on specific instances. I was never able to see my Pixelfed posts from fedia.social (ice shrimp), for example.

I was also able to search, follow, and see your Pixelfed posts from mastodon.social.