I can't access the sandbox

Issue Symptoms

I am unable to log in to the sandbox account, my email address and password don't work.

Resolution Steps

It's possible that you are not yet listed as a member of the sandbox account.

When the owner or an admin creates a premium sandbox, agents are also copied. However, if they create a standard sandbox, this action only copies the owner and all existing admins' credentials. If they added or upgraded you to admin after they created the sandbox, this account won't include your current profile. In this case, the owner or any admin who has access to the sandbox will have to manually add you as a member or update your profile.
Ask the owner or an admin of your account to open the sandbox link and follow the steps in Adding agents and administrators. As a newly added user, you will receive the welcome email, which will allow you to accept the invitation and create an account. 

For more information, see the following article: Testing changes in your standard sandbox