Hi @pandas , 
I faced the similar issue and upon raising a support ticket to Databricks, got to know the root cause (based on the response received). 

In case your email address has some issues receiving the email when the invite is being sent, the email gets bounced and is added in Suppression list.

For me, when my email id was invited, the email id had access issues. So it went into suppression list. 

The support team released it from the suppression list and then I started getting invite email. 


Below is the text from the response of the ticket.
"Reason": "BOUNCE",

The reason for this could be one of these:

A soft bounce or a transient bounce is a bounced email that's rejected by the recipient mail server because of a temporary failure. Temporary failures that can lead to a soft bounce include:

• The recipient mailbox is full.

• The recipient mailbox is temporarily unavailable.

• The server limits are exceeded.

• The server is overloaded.