View Source

Open the API keys page at Stripe.
Copy the "Publishable key" from the "Standard keys" table and insert it at the WHMCS gateway configuration page.
Click the "Create restricted key" button and enable the following permissions:

Resource	Permission
Apple Pay Domains	Write
Balance transaction sources	Read
Charges	Write
Customers	Write
Customer session	Write
Events	Read
PaymentIntents	Write
PaymentMethods	Write
SetupIntents	Write
Sources	Write
Tokens	Write
Checkout Sessions	Write
Payment Links	Write

After the key has been created, insert the secret key at the WHMCS gateway configuration page.