Is Caddy running in the jail? service caddy status. If it isn't, start it with service caddy start. If you still get the same error, see if there's anything in caddy.log then.
i did service caddy restart. now the log looks like:
root@nextcloud:/ # cat /var/log/caddy.log
2019/10/27 03:41:16 [INFO][cache:0xc0001ca370] Started certificate maintenance routine
2019/10/27 03:41:16 [WARNING] Stapling OCSP: no OCSP stapling for [deni2.hopto.org]: no OCSP server specified in certificate
2019/10/27 03:41:16 [INFO] Successfully loaded TLS assets from /usr/local/etc/pki/tls/certs/fullchain.pem and /usr/local/etc/pki/tls/private/privkey.pem
Activating privacy features... done.
Serving HTTP on port 80
http://deni2.hopto.org
2019/10/27 03:41:16 [INFO] Serving
http://deni2.hopto.org
Serving HTTPS on port 443
https://deni2.hopto.org
2019/10/27 03:41:16 [INFO] Serving
https://deni2.hopto.org
2019/10/27 03:45:14 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer: )
2019/10/27 03:45:14 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer:
http://192.168.178.199/)
2019/10/27 03:46:33 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer: )
2019/10/27 03:46:41 http: TLS handshake error from 192.168.178.74:61996: no certificate available for ''
2019/10/27 03:46:43 http: TLS handshake error from 192.168.178.74:61997: no certificate available for ''
2019/10/27 03:46:44 http: TLS handshake error from 192.168.178.74:61998: no certificate available for ''
2019/10/27 03:46:45 http: TLS handshake error from 192.168.178.74:61999: no certificate available for ''
2019/10/27 03:46:46 http: TLS handshake error from 192.168.178.74:62000: no certificate available for ''
2019/10/27 03:46:47 http: TLS handshake error from 192.168.178.74:62001: no certificate available for ''
2019/10/27 03:46:48 http: TLS handshake error from 192.168.178.74:62002: no certificate available for ''
2019/10/27 03:46:54 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer: )
2019/10/27 03:49:12 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer: )
2019/10/27 03:49:15 [INFO] 192.168.178.199 - No such site at :80 (Remote: 192.168.178.74, Referer: )
2019/10/27 04:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 04:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 05:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 05:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 06:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 06:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 07:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 07:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 08:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 08:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 09:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 09:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 10:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 10:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 11:41:16 [INFO][cache:0xc0001ca370] Scanning for stale OCSP staples
2019/10/27 11:41:16 [INFO][cache:0xc0001ca370] Done checking OCSP staples
2019/10/27 12:32:17 [INFO] SIGTERM: Shutting down servers then terminating
2019/10/27 12:32:17 [INFO][cache:0xc0001ca370] Stopped certificate maintenance routine