Horizon: You are not authorized for any projects or domains.

[AJNOURI]

Though the user is created:

openstack user create --email "user3@domain1" user3 --domain domain1 --password-prompt

User Password:
Repeat User Password:
+---------------------+----------------------------------+
| Field | Value |
+---------------------+----------------------------------+
| domain_id | b27c4d5ab21240a8979397f107515b1c |
| email | user3@domain1 |
| enabled | True |
| id | 1c3f7243130d44fcb42c8ed2901990c1 |
| name | user3 |
| password_expires_at | None |
+---------------------+----------------------------------+

[AJNOURI]

Looking at the existing roles and projects (in the appropriate domain)

openstack role list

+----------------------------------+---------------+
| ID | Name |
+----------------------------------+---------------+
| 16a9f7d9e01941c08fc52a486a431057 | ResellerAdmin |
| 47db593671d74890b62b0f39f2890fa0 | SwiftOperator |
| 822f0dd4c7fd4cc480507a1f9bd61281 | admin |
| 9fe2ff9ee4384b1894a90878d3e92bab | member |
+----------------------------------+---------------+

openstack project list --domain domain1

+----------------------------------+------------+
| ID | Name |
+----------------------------------+------------+
| d9fb488a66d540058c7cda0bb726fb91 | d1project1 |
+----------------------------------+------------+

openstack role list --domain domain1
openstack role list

+----------------------------------+---------------+
| ID | Name |
+----------------------------------+---------------+
| 16a9f7d9e01941c08fc52a486a431057 | ResellerAdmin |
| 47db593671d74890b62b0f39f2890fa0 | SwiftOperator |
| 822f0dd4c7fd4cc480507a1f9bd61281 | admin |
| 9fe2ff9ee4384b1894a90878d3e92bab | member |
+----------------------------------+---------------+

Note that roles appear only within the default domain "default" because they are unique globally.

So assigned the default role "member" and a project to the created user
openstack role add --project d1project1 --user user3 --user-domain domain1 _member_

Now successfully logged in to Horizon dashboard with the user:

[AJNOURI]

Another alternative issue:
The user doesn't belong to the project/domain