Inquiry about grafana display issue

Dear team,

We are using PromQL probe_ssl_earliest_cert_expiry{c_http="$HTTPS"}-time()
To display the certification expiration status. But some urls can display number, but some cannot.

When we check the result in Prometheus, for example,, in Prometheus, it displays as bellow, and do have value, which cannopt display in Grafana dashboard:

Would you please help to advise what might be the root cause? Thank you.