Using template: AWS/Deploy-ECS.gitlab-ci.yml on a DotNet5 webapp and using start guide

I have tried using the the ruby rails template and it works, so Im not sure if this is related to DotNet5

When the pipeline runs i get the error below:

Status: Downloaded newer image for heroku/pack:18
===> DETECTING
ERROR: No buildpack groups passed detection.
ERROR: Please check that you are running against the correct path.
ERROR: failed to detect: no buildpacks participating
ERROR: failed to build: executing lifecycle: failed with status code: 100
Uploading artifacts for failed job
00:00
Uploading artifacts...
WARNING: gl-auto-build-variables.env: no matching files 
ERROR: No files to upload                          
Cleaning up project directory and file based variables
00:01
ERROR: Job failed: exit code 1