Share dash board - problems

I have a Power BI user, extended to Power BI Pro with currently 134 days left.

I shared a dashboard to this user, starting from a complete Power BI pro user,
but when under the inscription:

Grant access to:

I enter the first e-mail address I always get the message:

'One or more e-mail addresses with the following domains are external to the organization: myorganization.it'

(which is not true, because the address belongs to the organization)

thanks