Notifications not showing in Apple Watch

I have recently purchased Apple Watch Series 9 Cellular version. I am facing issues in getting notifications on my watch. The notifications are either delayed or skipped for some applications. It is too annoying to invest time in such a successful device of Apple. I showed to Apple service center and they said there is no issue in the watch based on some tests. I plan to use my watch along with Wifi when at home and Cellular while moving out. Bluetooth is my last option that i plan to use to connect and get notifications. I am up to date with latest OS in Watch and Phone. Tried multiple times re-pairing, turned off DND or any other setting that would disable notifications. Please if anyone has a solution, please revert.