AWS EC2 review button disabled

I'm trying to put the default Docker container online on the AWS EC2 with the default options.

The four first steps have been successfully done:

• Step 1: Welcome to Amazon ECS
• Step 2: Create Task Definition from sample
• Step 3: Schedule Tasks
• Step 4: Configure Cluster
• Step 5: Review

At step 4 however, the "Review and Launch" button is disabled and no warning message is displayed.

While trying to solve the problem, I've noticed that the documentation explains how to solve the problem:

... the Review and Launch button is disabled and you must do the following:

1. Click Next: Configure Instance Details.

2. Select your VPC from the Network list and select a subnet from the
   Subnet list.

3. Select Enable from Auto-assign Public IP. Note that Enable is the
   default only if the VPC is a default VPC.

There is however no "Next" or "Configure instance Details" button on my interface.

How can I get to step 5?