Please add juliusarden:subdomain-login into your ./meteor/packages before accounts-base in order for it to work on first page visit.
On your settings, set the domains (required) and other optional fields
// settings.json
{
...
"subdomainLogin": {
"domains": **["<<YOUR_DOMAIN_HERE>>", "<<YOUR_OTHER_DOMAIN>>"]**,
"expiresAfterDays": 30,
"cookieName": "subdomain_token",
"secure": true,
"debug": false,
"ignoreLocalStorage": false, // If you want to ignore the default localStorage completely and just use cookie.
},
}
Inspired by jfrolich meteor subdomain persistent login