The systems will redirect constituents to the site's default homepage after a password reset or login. If the constituent is seeing a page not found error, then the issue is likely because the homepage specified in your site is unpublished. By default, your homepage is set to a Pagebuilder page called "homepage." Below are the steps to publish it.
  1. Go to Content > PageBuilder
  2. Search "homepage"
  3. Next to homepage, click Manage
  4. Next to the desired page version, click Publish
Related topic: How do I update the default site homepage?