A drop in Domain Authority (DA) can happen due to several reasons:

Lost Backlinks: Losing high-quality backlinks reduces your DA. Monitor and regain valuable links.
Low-Quality Backlinks: An influx of spammy links can harm your DA. Disavow toxic links.
Competitor Gains: Competitors gaining more high-quality links can lower your comparative DA.
Website Changes: Major changes like redesigns or URL updates can impact DA. Ensure SEO best practices.
Content Issues: Outdated or low-quality content affects engagement and backlinks. Regularly update content.
Technical SEO Problems: Issues like slow loading times or broken links can affect DA. Conduct regular audits.
Algorithm Updates: Stay updated on search engine algorithm changes and adjust your strategy accordingly.
Moz Algorithm Changes: Moz’s updates to DA calculations can cause fluctuations.
To recover, focus on improving content quality, building high-quality backlinks, and addressing technical SEO issues.