Welcome to the Q&A Forum

I'll help you and tell you more about your issue you can contact me here Help

To solve a SERP title display issue, follow these steps:

Check and optimize your HTML title tags (keep them within 60-70 characters).
Use relevant keywords in your titles.
Ensure unique titles for each page.
Implement structured data for rich snippets.
Use clear and descriptive titles.
Review and improve meta descriptions.
Check for HTML errors.
Monitor Google Search Console for issues.
Use "Fetch as Google" to view how Googlebot sees your pages.
Update and resubmit sitemaps when making changes.
Be patient for search engines to update their index.
Addressing these points should help resolve most SERP title display problems.

Yeah i'm also trying to increase domain authority but it's difficult for me can you please guide me?