I just shared a dashboard and some users got the notification while others not. The other problem is that the users who did get the notification, they get into a gray screen when they click on the 'Go to dashboard' button.
I have a premium account.
For the users who didn't receive the notification, please cancel invite for them then share the dashboard again, ensure the option is enabled Send email notification to recipients when sharing.
For the issue that the grey screen shows when open the dashboard, I would suggest you let the users open the inprivate browser, type app.powerbi.com and sign in with their account. Copy the link from Go to Dashboard button then paste in the inprivate browser to see if the dashboard can display fine.
Best Regards,Qiuyun Yu