Customers not receiving tracking number

[VeraYang]

I purchased the labels from the order page, it marks shipped.  However, none of my customers receive the tracking number so I did a test purchase myself, I did not receive the tracking information either.  under website-email, text alert are all checked, 
one more thing, there's no tracking information when the customers go to the order status page.  

[MayaP]

Hey @VeraYang  — I definitely want to make sure your customers receive their tracking information.

Could you share a few order numbers where this happened so I can take a closer look and investigate further?

[VeraYang]

Hi,  I just did a test order # 560221010.  
Customer received the receipt. 

I did split order and printed two UPS label from the dash board.

Customer did not receive tracking numbers emails.

Customer received text message for ONE tracking number.

tracking numbers can not be found when the customer go to order status page.