SSH times out when building a Windows image using amazon-ebs

I’m trying to set up a Windows image on EC2. However, SSH times out; here’s what happens when I try:

PS C:\Users\Jesse\Infrastructure> packer build .\template.json
amazon-ebs: output will be in this color.

==> amazon-ebs: Prevalidating any provided VPC information
==> amazon-ebs: Prevalidating AMI Name: packer-example 1605725857
    amazon-ebs: Found Image ID: ami-02b5cd5aa444bee23
==> amazon-ebs: Creating temporary keypair: <redacted>
==> amazon-ebs: Creating temporary security group for this instance: <redacted>
==> amazon-ebs: Authorizing access to port 22 from [] in the temporary security groups...
==> amazon-ebs: Launching a source AWS instance...
==> amazon-ebs: Adding tags to source instance
    amazon-ebs: Adding tag: "Name": "Packer Builder"
    amazon-ebs: Instance ID: <redacted>
==> amazon-ebs: Waiting for instance (<redacted>) to become ready...
==> amazon-ebs: Using ssh communicator to connect: <redacted>
==> amazon-ebs: Waiting for SSH to become available...
==> amazon-ebs: Timeout waiting for SSH.
==> amazon-ebs: Terminating the source AWS instance...
==> amazon-ebs: Cleaning up any extra volumes...
==> amazon-ebs: No volumes to clean up, skipping
==> amazon-ebs: Deleting temporary security group...
==> amazon-ebs: Deleting temporary keypair...
Build 'amazon-ebs' errored after 6 minutes 6 seconds: Timeout waiting for SSH.

==> Wait completed after 6 minutes 6 seconds

==> Some builds didn't complete successfully and had errors:
--> amazon-ebs: Timeout waiting for SSH.

==> Builds finished but no artifacts were created.
PS C:\Users\Jesse\Infrastructure> 

Here’s my template.json file:

  "min_packer_version": "1.6",
  "variables": {
    "aws_access_key": null,
    "aws_secret_key": null
  "sensitive-variables": [
  "builders": [
      "type": "amazon-ebs",
      "access_key": "{{user `aws_access_key`}}",
      "secret_key": "{{user `aws_secret_key`}}",
      "region": "us-east-1",
      "source_ami_filter": {
        "filters": {
          "virtualization-type": "hvm",
          "name": "Windows_Server-2019-English-Full-Base-2020.11.11",
          "root-device-type": "ebs"
        "owners": [
        "most_recent": true
      "instance_type": "t2.micro",
      "ssh_username": "Administrator",
      "communicator": "ssh",
      "ami_name": "packer-example {{timestamp}}",
      "disable_stop_instance": "true",
      "launch_block_device_mappings": [
          "device_name": "/dev/sda1",
          "volume_size": 50,
          "volume_type": "gp2",
          "delete_on_termination": true

No provisioners yet; I’m just trying to get the thing built first. Any idea what I’m doing wrong?