These are a few of the most common reasons for contract and invoice errors:
Are you an Admin user? Your company needs to grant you Admin privileges to generate contracts and invoices
Have you completed your Stripe pay-to account on your My Wallet page? This information is required for sending invoices (we want to be sure to know where to pay you!)
Have you recently updated your email address? If so, be sure to verify it (look for an email in your inbox) before you can take further action in your account