Contact still not recorded in sendinblue

I use a Material Design plugin which forced me to format the thing like that:

[md-for]
...
[group group-001]
...
[md-text label="Your email"]
[email* your-email]
[/md-text]
[md-checkbox label="Subscribe to our newsletter"]
[checkbox sendinblue-opt-in default:1 "Subscribe"]
[/md-checkbox]
[hidden sendinblue-list-id "5"]
...
[/group]
...
[/md-form]

Checkbox is well displayed but contact are not recorded in Sendinblue.
Would you know how to fix that maybe..?

Best!
Simon