Thank you for your answer. The service is up again now. But due to the outage, I have reached a rateLimit.
Type: urn:ietf:params:acme:error:rateLimited
Status: 429
Detail: Error creating new order :: too many certificates already issued for exact set of domains: *.emig.me,emig.me: see https://letsencrypt.org/docs/rate-limits/
How can I fix that?