Looking for logging into the Crm User Portal site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Crm User Portal site. After that you can login as usual with your login credentials.
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/portals/configure-portal-authentication
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/portals/administer-manage-portal-dynamics-365
https://community.dynamics.com/crm/f/117/t/217106
https://community.dynamics.com/crm/f/117/t/283183
https://community.dynamics.com/crm/f/117/t/265474
https://community.dynamics.com/crm/f/117/t/239979
https://www.appjetty.com/dynamicscrm-portalnest-customer-portal.htm
https://www.appjetty.com/dynamicscrm-customer-portal.htm
https://www.crmportalconnector.com/developer-network/documentation/how-tos/mvc-based-widgets/how-to-create-a-portal-user-from-crm
https://www.preact.co.uk/blog/how-to-get-started-with-dynamics-365-web-portals
https://community.adxstudio.com/learning/demo-guides/login-with-administrator-account.pdf
https://crmbook.powerobjects.com/extending-crm/portal-options-and-considerations/types-of-authentication/
https://www.vtiger.com/all-in-one-crm/customer-portal/