My latest post doesn't show on my site homepage

try:

-deactivating ALL plugins temporarily to narrow down and possibly fix the problem. If the problem goes away, activate them individually (one-by-one) to find the problematic plugin.

-switching to the default theme (“twentyten”) for a moment by renaming your current theme’s folder in wp-content/themes. The idea is to force WordPress to fall back to the default theme to rule out any theme-specific issue.

–if that does not resolve the issue, you may try increasing memory available for php.