Sales Order Approval Notification Email are not going to Approver

Summary:

Hi,

I have defined "Sales Order Approval Rule" depending on "Assign to Manager" approvers.

When I submit the order I can see "View Approval Information" means Approval Rules trigger the Notification,

But actual emails are not coming to user. Also they can't see the notification on top right corner at Bell icon.

Anybody knows what is missing. I checked all the setups but not able to find out.

Appreciate your help on this.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):