renovate/lib/modules/manager/argocd

The argocd manager has no fileMatch default patterns, so it won't match any files until you configure it with a pattern. This is because there is no commonly accepted file/directory naming convention for argocd YAML files and we don't want to check every single *.yaml file in repositories just in case any of them have ArgoCD definitions.

If most .yaml files in your repository are argocd ones, then you could add this to your config:

{
  "argocd": {
    "fileMatch": ["\\.yaml$"]
  }
}

If instead you have them all inside a argocd/ directory, you would add this:

{
  "argocd": {
    "fileMatch": ["argocd/.+\\.yaml$"]
  }
}

Or if it's only a single file then something like this:

{
  "argocd": {
    "fileMatch": ["^config/applications\\.yaml$"]
  }
}

If you need to change the versioning format, read the versioning documentation to learn more.