This case is mostly based on the hosting settings. Your host have disabled the possibility to put your site into an iframe. Solution: check your hosting settings and adjust this by yourself or ask your hosting provider to enable embedding your website as an iframe for you.

The second possibility is, that you have not assigned the custom url to some user role. Please check the user role checkboxes in the Dashboard Switcher settings.

This is caused by your Wordpress settings. Just turn of the admin toolbar for this user you are looged in and then it wont show the toolbar anymore. Here are some other solutions for not showing the toolbar: Solution 1: You disable the admin toolbar based on a userrole (https://wptavern.com/wordpress-tip-disable-the-toolbar-on-a-per-user-role-basis) If you like you can make a custom userrole and give the userrole admin rights aswell but disable the admin bar only for this specific userrole. Solution 2: You remove the admin bar on the specific page only, which you can do with a function (https://second-cup-of-coffee.com/hiding-the-wordpress-admin-bar-on-certain-pages/) Solution 3: You set up a subdomain and wordpress install. On this seperate wordpress install you create the pages which then you want to show in your clients website. The pages should have some encrypted url. for example: https://subdomain.webcompany.com/CRsxCBG9aAgZnvgm09fIal/ And turn on "noindex" for the website so that google will not list it. With this setup you can easily implement the same url on all ur client sites and you save time cause you can make changes on this page and all clients will see the change. And the chance that a stranger will see the url is nearby 0.

If you can not login with your email address, please contact me. Write me your e-mail address you used for the purchase of Dashboard Switcher and i will activate the client login for you manually.

1: First of all you should activate "noindex" for the pages you use as a weclome screen or widget.
2: I recommend you to use a long, complex url path. Example: https://www.mywebsite.com/welcome-2021-screen3342.
3: You should remove the page from your wordpress sitemap (here is some instruction on how to do it https://betterstudio.com/blog/yoast-seo-exclude-page-from-sitemap/)