The Shared Google Assets do not allow access unless the account is a registered Google account.
In order to share or access anything from the Google ecosystem of shared tools , the external account either needs to be setup within the Google ecosystem, or needs to be registered with Google.
If it is already a Google account, then there should not be any issues.
However, if the account needs to be registered with Google, then follow the directions below, or copy the information, and send them to the person who needs access.
Navigate to the Google Account setup page :: https://accounts.google.com/signin
Because it's Google, there are always a couple of different options available that the link above could end up sending you.
** Click on the Create an Account option in the upper right corner
** Click on the Create Account option in the lower right, then the “For my personal use” option
Both options will take you to the same place.
Fill in the necessary information, and click the NEXT button
When prompted to choose an email address based on your name, click the option that reads: USE YOUR EXISTING EMAIL
On this page, you will be able to enter your work email address to link it to Google. Then click NEXT
This will start the confirmation process. An email will be sent to that address with a 6 digit code. That code will need to be entered into the space provided. Once the email is received, copy the code into the space provided, and click next.
You will be prompted to create a password for the account. DO NOT use the same password as your email account.
Finally, click NEXT to complete the link, and agree to the Google Terms of Service.
This account can now be used to access Google account services.