If you are unable to access the ChartMogul Admin section, it means that you do not have sufficient rights. Contact the account owner or an admin of your ChartMogul account to get the Account Token and Secret Key.
If the authentication credentials that you provide are incorrect, then the account will not be connected and the following error will be shown.
Close the dialogue and enter the correct credentials to connect your account.
Currently, ChartMogul's Zapier integration doesn't include an action to create customers. But ChartMogul has created a guide on how this is still possible, using Zapier's Webhooks: https://help.chartmogul.com/hc/en-us/articles/115000304529-How-to-use-Zapier-to-push-new-trial-customers-from-Hubspot-to-ChartMogul