Zeptomail stopped working

Zeptomail stopped working

Hi, Zeptomail was working fine, and then suddently it stopped working. 
No more email are sent, we did not change any setting.

When we try to send a email via Zeptomail SMTP, on our nodejs server, we get after a while:
 Error: Connection timeout

What is wrong ? It was working before it suddently stopped today. We still have credits.