Sending Email From Contact Us web site page after setting Gmail

When I am trying to send email from ERPNext I get this log error:
inspect = <module ‘inspect’ from ‘/usr/lib/python3.10/inspect.py’>
msg = ‘Encryption key is invalid! Please check site_config.json’
raise_exception = <class ‘frappe.exceptions.ValidationError’>
frappe.exceptions.ValidationError: Encryption key is invalid! Please check site_config.json