Why your members cannot log in
When the forum is embedded into a page, the cookies that it sets become third-party cookies since it is not the main page that was requested in the browser address bar.
The Safari browser blocks third-party cookies by default. Members who open your website in Safari may be taken to the login page instead of the forum, or may be signed out again right after they log in. The forum works normally in other browsers.
Connect your domain to fix the problem
Connect your domain to your forum so that your forum and your website use the same root domain. For example, forum.yourdomain.com for a website at yourdomain.com.
Safari then considers the cookies first-party, so they are always accepted and members stay logged in. If your domain host is not listed, see the instructions for each domain provider. You can also make your forum use a subdomain of your website's domain name, which reaches the same result.
What happens while your domain is not connected
When the Safari browser is used to view an embedded forum for the first time, the page will first redirect to the forum so that it becomes first-party and then it will redirect back to the embedded forum. This ensures that the Safari browser accepts cookies from the forum so that users can log in and use the functionality as normal.
The redirect will only happen the first time the user visits the forum using the Safari browser. If Safari still doesn't accept the cookies, the forum will automatically open as a full page instead of as embedded. These redirects are all avoided once your domain is connected to your forum.
Wix and Google Sites
The embed code is not supported on Wix or Google Sites. If your website is built on one of these platforms, link to your forum instead of embedding it. See how to add your forum to a Wix website or how to add your forum to a Google Sites website.