User Syncronization limitations on single sign on

I am running a Wordpress homepage with several sub-sites.

I have installed the User Syncronization plugin but it apparently cannot make the master domain share cookies with other sub-sites.

This makes users to login each time they visit another subsite.

I need to make users to be automatically signed up for all sub-domains upon signing up on the master domain.

I have seen people discussing on the issue on this support forum and elsewhere as Cross Domain Cookie Sharing for WordPress.

However, I don't know how to do coding and none of the information has helped me to succeed in having an automatic sync login across all my subdomains.

I'd appreciate it if someone can help me achieve automatic user sync across all my subdomains.

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