Hi,
First things first, it's a common misconception that the robots.txt disallow: / will prevent indexing. It's only indented to prevent crawling, which is why you don't get a meta description pulled into the result snippet. If you have links pointing to that page and a disallow: / on your robots, it's still eligible for indexation.
Second, it's pretty weird that the noindex tag isn't effective, as that's the only sure-fire way to get de-indexed intentionally. I would recommend creating an XML sitemap for all URLs on that domain that are noindex'd and resubmit that in Search Console. If Google hasn't crawled your site since adding the noindex, they don't know it's there. In my experience, forcing them to recrawl via XML submission has been effective at getting noindex noticed quicker.
I would also recommend taking a look at the link profile and removing any possible links pointing to your noindex pages, this will help future attempts at indexing.