Yes, this is a common issue, and I don't know why Microsoft doesn't have an official article for this yet.
When you create a Power Page, a mailbox named after the page is automatically created. This is the email address used for invitations, password resets, email verification.
This email address needs to be setup on Dynamics 365 with the appropriate licenses to send out emails. However, I think Microsoft is having issues with this as we currently have a support ticket open with them.
Refer to this solution for how to access Dynamics Re: Power Pages not sending email confirmation ema... - Power Platform Community (microsoft.com)
As a workaround you can setup the Dynamics to use your own email as the sender instead of the one mentioned above.
How to check if the email is setup correctly:
1. Go to the Power Pages portal
2. Find Contacts in the menu on the left, and find the account
3. Make sure you're in active contacts/all contacts
4. Select the contact
5. Make sure you're in Portal Contact
6. Go to Notes & activities and scroll down. You should be able to see the email you expected to receive.
Hope this helps and please accept this as a solution if it worked!
