Hi Vijay!
Sharing a couple of thoughts, please do check which are relevant for inspection.
• If the domain itself has been changed like you mentioned, wouldn't that be the reason for a different score? You are essentially pointing search engines to a new address, a young domain in comparison with not much activity, so it would be like starting from scratch
• Also, please check for page duplication issue for www and non-www version of the same page(s). It's best to stick to one and add canonical to prevent duplication. (We've stuck to non-www versions. )
• Lastly, as you know the domain authority and score are developed by individual SEO tools and mostly comes handy when folks evaluate for backlinks. A suggestion is to not be alarmed with it or use that as a strict metric of progress. But As the website scales, do monitor spam scores to ensure decent backlink hygiene! :)