The above url is giving us a secure error. It worked fine 3 days ago, certificate is up to date, nothing changed. (the Let's encrypt certificate is generated via their server when you select generate Let's Encrypt)
We contacted the server people for support but they said it might be that our domain is banned?
That website appears to be misconfigured. It is serving an intermediate only, and not a leaf certificate.
If you were banned, you would see an error in your ACME clients logs when you request the cert, and not an error when you try to connect to the website.
If you want more help, you will have to tell us what webserver you are using, how it is configured, and you obtained the certificate.