Urgent Google Indexing Fix

I’m looking for someone who can quickly diagnose why 324 of my blog-type pages still sit in “Discovered – currently not indexed” limbo while only 68 URLs show up in Google. There have been no recent URL or structural changes, and a sitemap is already live and submitted through Search Console... (Budget: $2 - $8 USD, Jobs: Content Strategy, Google Search, Google Webmaster Tools, Next.js, React.js, Search Engine Marketing, SEO, SEO Auditing, Web Crawling, Website Optimization)