As of today, Google have stopped supporting the mobile sync feature for new devices when using a personal account (it will still work for those who already have mobile sync installed and working).
If you have a Google Apps for Business or Education account you can continue to use Google Sync tool but there is an even easier way to sync your Google calendars and iCal on your iPad and iPhone (or both)
Below is the easiest and most stable way to sync your Google Calendars and iCal:
Open settings on your iPad or iPhone
Click on the Mail, Contacts, Calendars button on the left hand side
You will see an accounts section that has iCloud, Exchange etc. At the bottom of the Accounts section click on Add Account…
Select the Gmail option
Enter in your details. The email address is the email address that your calendars are associated with.
If you have several calendars associated with different Gmail accounts I would suggest you choose one Google account to be your primary account and then share all your calendars with that account.
When you do this, you can still see all your individual calendars but you can also make the most of the layering feature of Google Calendar where you can see multiple calendars all at the same time.
A couple of things to note:
1. The name doesn’t have to be your actual name. You can enter whatever you would like the recipient to see when they receive your email.
2. If you use 2-step verification make sure you enter the application specific password, not your regular password in the password section
Click next at the top of the screen and wait for the account to be verified. Once your account is verified you will see that you can turn the different Google products on or off. Make sure that you have the calendar option turned on.
Open up your calendar on your device and the sync will automatically begin.
If you have multiple calendars…
If you have multiple calendars set up (even if they are in the same Google account) you will need to complete one more step.
If you have a personal account go to https://www.google.com/calendar/syncselect and select the calendars you would like to sync
If you have an Apps for Business or Education account you can go to https://www.google.com/calendar/hosted/your_domain/syncselect, (replacing ‘your_domain’ with your actual domain name)
Once you have established the sync between Google calendars and iCal you will be able to update your calendars on any device and automatically transferred to all your devices.