Thanks for signing up for the cloud trial, and I’m sorry you run into trouble logging in to your instance.
I recommend you create another admin user account, and use this account to reset the password of your original account.
To do this, login to your octopus account, click on your instance, then click on the New user invite button. This will send you a link to create a new admin user for your instance.
After resetting the password for your original account and have verified that you can login to your original account you can delete this newly created account from within your Octopus Cloud Server instance.
Hope that helps, and please let me know if you have any other issues or questions.