There's no official way to get Google to reevaluate a landing page. As per their own instructions on this:
The Google Ads system visits and evaluates landing pages and websites on a regular basis. If you make significant changes to improve your landing page experience, you may see higher ad quality (and higher Ad Rank) over time. You might not see an immediate impact, but you may see results within days or weeks.
From experience, it usually takes around 14 days to see changes reflected in the Landing Page Experience metric.
However, that being said, there is a way I have found that triggers Google to reevaluate pages much quicker. Google will evaluate a new landing page almost immediately. So if you change the URL of the landing page and update your ads accordingly, Google will update their evaluation much quicker. You'll usually see the landing page experience rating update within 2 to 3 days if you do this.
Do be aware, if you are also using this page as part of your SEO strategy, changing the URL can have negative consequences here, so bear that in mind.