Manychat + Make: “Send a Flow” returns a validation error even with a valid Subscriber ID

I'm having trouble getting my Manychat automation flow to work.

Here is the context:

My sales funnel follows the classic model: I sell a low-ticket product, followed by an upsell offer for customers who purchase the low-ticket product.

I offer the low-ticket product to prospects through a WhatsApp approach, sending a message to the buyer immediately after the purchase is confirmed. The idea is to use the Manychat platform for this purpose.

To receive the webhook from my sales platform, I use the Make automation platform (make.com).

My Make automation flow is set up as follows:

1. The sales platform sends a webhook to Make;

2. Make receives the webhook via URL and passes the information to the Manychat Create Subscriber module within Make. The phone number and WhatsApp information are passed in order to create the contact in Manychat;

3. From the Create Subscriber module, the flow continues to the Send a Flow module. The Subscriber ID and the ID of the automation to be triggered are passed here. The Subscriber ID comes from the data.id variable generated by the previous Create Subscriber module, while the automation ID comes from a portion of the automation URL, starting with the word "content";

4. This is where the problem occurs: when I pass the data.id parameter into the Subscriber ID field of the Send a Flow module, the parameter generates a validation error. In addition to trying to pass the data.id value directly into the field, I have also tried several conversion functions, such as parseNumber, toString, replace, and trim, as well as combinations of these functions, but nothing has worked.

I need help figuring out how to successfully use this function.