I am working on my first for and when I try to preview it I get this message: "Form not found"

I have checked and you account is autosuspended by our phishing system. Because of that your are getting "Form not found" message. Your account is suspended because of your imported form. Inside of that form there is a password field and it is against our terms of use to collect login credentials (such as password). 

Phishing. You agree that Company may terminate your JotForm Service immediately if a form's purpose is found to be deceptively obtaining: sensitive credit card information, social security numbers, user login credentials, or other sensitive personal information. All these activities are considered as Phishing and any account along with the violating forms will be suspended immediately.

I saw that you have deleted that form and that form is now located inside of Trash folder on your account. I have Purged that form and I have activated your account. Form that you created is now working. 

Let us know if you need further assistance.