After disabling IPv6:
[Tue May 21 19:04:57 CEST 2019] Pending
[Tue May 21 19:04:59 CEST 2019] Pending
[Tue May 21 19:05:02 CEST 2019] Pending
[Tue May 21 19:05:04 CEST 2019] Pending
[Tue May 21 19:05:07 CEST 2019] Pending
[Tue May 21 19:05:09 CEST 2019] Pending
[Tue May 21 19:05:12 CEST 2019] Pending
[Tue May 21 19:05:14 CEST 2019] Pending
[Tue May 21 19:05:17 CEST 2019] Pending
[Tue May 21 19:05:20 CEST 2019] pics.domain.com:Verify error:Fetching
https://pics.domain.com/.well-known/acme-challenge/pGEVLMGkmxyDcpnQkSbuto5WnAgTbWXRuMH4m2cKDhM: Timeout during connect (likely firewall problem)
[Tue May 21 19:05:20 CEST 2019] Please add '--debug' or '--log' to check more details.
[Tue May 21 19:05:20 CEST 2019] See:
https://github.com/Neilpang/acme.sh/wiki/How-to-debug-acme.shSubdomain is normally reachable via browser.