Share feature not working

Share feature not working

When I share my calendar the end user is getting the email from Zoho to sign up, but is not seeing the shared calendar in their calendar feild. Is there a limit to how many people can use a shared calendar? Are there issues with shared calendars for people using Mac? I'm a loss as to why it's suddenly not working as I've been using this calendar with a group for over a year. Now when I try to share with new people, it does not work. Please help!