Since ,you try all. Look below suggestion .one of them you may not tried earlier ,my work for you.
1. Disable Battery Optimization (Unrestricted)
Samsung’s "Deep Sleeping" feature can kill Gmail's background process.
Long-press the Gmail icon on your home screen and tap the "i" (App Info) icon.
Tap on Battery. Select Unrestricted. (By default, it is usually set to "Optimized," which can delay or block notifications). 2. Enable "Manage Notification Categories"
In recent One UI versions, Samsung hides specific app notification toggles by default.
Go to Settings > Notifications > Advanced settings. Scroll to the bottom and ensure Manage notification categories for each app is toggled ON.
Now, go back to App info for Gmail > Notifications > Notification categories.
Make sure every account and category (like "Mail") is set to Alert and not "Silent."
3. Change Gmail Internal Sync Settings
Sometimes the app is set to sync the mail but not actually alert you for it.
Open the Gmail app > Tap the three lines (Menu) > Settings.
Select your specific Email Address. Tap Inbox notifications. Ensure Notify for every message is checked. (If this is unchecked, you will only get notifications for what Google deems "Important").
4. Remove from "Deep Sleeping Apps" Go to Settings > Battery > Background usage limits. Check Deep sleeping apps. If Gmail is in this list, remove it immediately. Apps in this list will never run in the background unless you open them.
5. If none of these work, try clearing the Cache (not Data) of the Google Play Services app, as this handles the "push" delivery for all Google notifications.
Open Settings → Notifications → Advanced settings → Enable “Manage notification categories for each app.” Then go inside Gmail notification categories and enable Mail / Labels / Sync notifications.
As per your query, we request you kindly share the log file. Also, share video clips and images for better understanding. This will help us to investigate further and resolve this issue.
Samsung Members Application (Open Samsung Members Application > Support> Tap on send feedback> Choose Composer> Select error report> select the appropriate issue category> Type your query and send.)
Note: To ensure relevant log information is included in the error report, submit the report within 3 minutes of encountering the bug or error, and do not terminate (swipe away) the Samsung Members application until you are notified that the report has been sent. This can take up to 5 minutes.
