A Herald Premium subscriber can log in on up to 4 different devices (e.g. personal mobile, work computer, personal tablet). If you log in on a fifth device or browser, the first device or browser you logged in to will lose access.
Subscriptions are for individual use only and user ID/password should not be shared with others (see Digital subscription T&Cs). If you need access for 5 or more people you can sign up for a corporate/group subscription.