Apple Watch Ultra doesn't show preview for some applications

Hi

I have a new Apple Watch Ultra (My first apple watch).

I have 3 applications I'm used to getting notifications (Banners, Notification Center, and Lock screen preview) without sound: Outlook, Slack and Gmail.

For these 3 apps, whenever there is a new notification, I'm not seeing any preview in my Apple watch. I'm only seeing the Red Dot appearing at the top of the screen, and can scroll down and see the notifications.

Why can't I see the preview?

I've also made sure that the Show Previews settings on my iPhone for all apps are "Always (Default)".

Thanks