Travis reject requests because of "does not have an active subscription"

Travis CI Discussions & Feedback
1

Get Owner XXX does not have an active subscription. on a public repo in “requests” page.
When I try to rebuild one job under a “build” page, I got this 403 response from Network:

{
  "@type": "error",
  "error_type": "error",
  "error_message": "Builds have been temporarily disabled for private repositories due to a insufficient credit balance"
}

See: https://app.travis-ci.com/github/fortanix/rust-mbedtls/requests