There is a bug that causes posts not to show in tags pages.
Before sending a Support in, check the post does not have more than 12 tags + categories together. If it does, drop the number to 12 and re-save the post.
Please really do check the tags pages.
When you contact Support, send the full POST address. Please do not say "it's all of them", or "just check" - I need the exact address. Not sending this makes the reply to you that much slower.
If your blog is marked Mature, I will tell you.
Contrary to what some are saying, this is not censorship or anything even remotely like it. It's a bug and one we will fix.