Hi @Lauriane
Thank you for posting.
According to your description, you want to filter the rows that less than 7 days before the due dates and send an notification.
I create a Flow and can achieve your needs
You can refer to the screenshots as below:

Expression:formatDateTime(addDays('1899-12-30', int(item()?['Expirydate'])), 'yyyy-MM-dd')
Expression:addDays(utcNow(), 7, 'yyyy-MM-dd')

Expression:formatDateTime(addDays('1899-12-30', int(item()?['Expirydate'])), 'yyyy-MM-dd')


This is my excel:

After flow runs, I will receive a notification as below:

Hope the content above may help you.
Best Regards
Lily