I am integrating PayPal for subscription related service, I have earlier implemented for single time payment by adding the Paypal button via adding the script
<script src="https://www.paypal.com/sdk/js?client-id=SB_CLIENT_ID"></script>
but for subscription as per the documentation
https://developer.paypal.com/docs/subscriptions/integrate/#subscriptions-with-smart-payment-buttons we are supposed to add
&vault=true&intent=subscription
also thus making it
<script src="https://www.paypal.com/sdk/js?client id=SB_CLIENT_ID&vault=true&intent=subscription"></script>
but after adding this I get the following error in the chrome console and the login page reloads indefinitely
Failed to load resource: the server responded with a status of 400 (Bad Request)
There seems to be a typo in your second snippet, client id
in place of the correct parameter name.
This sandbox URL works fine:
https://www.paypal.com/sdk/js?client-id=test&vault=true&intent=subscription