Thank you for reaching out to us. Unfortunately, since these different inbox tabs are completely on the user's end in gmail, there's nothing we can do from our end.
As Frankie has suggested, communicating to your contacts that they'll need to manually move at least one of your emails to Primary, should get Google's algorithm to accept your emails as Primary inbox material.
The most absolute solution would be for your contacts to get rid of their Promotions tab altogether. While I personally practice this, I do know that some Gmail users prefer their system automatically sorting emails based on the info within.
This all essentially comes down to the way Google's algorithm marks emails from us and similar email service providers. Ultimately, unless your contacts get rid of their Promotions tab or manually move at least one of your emails to their Primary tab, there's nothing that can be done on our end or yours. I apologize for any inconvenience this causes.
If you've any other questions or concerns, feel free to reply here or create a new thread. We'll be happy to assist. Have a lovely weekend!