Kimsufi / ispconfig 3.1 debian / seafile does not work

Hello,
I can not run seafile on a debian server with ispconfig 3.

I used several tutorials

however, on http ://seafile.boschetti.pro:8000 I always arrive on the same ERR_CONNECTION_REFUSED error page

I watched the logs :

> [Sun Sep 01 19:38:22.057972 2019] [proxy:warn] [pid 11411] [client 88.161.215.60:65231] AH01144: No protocol handler was valid for the URL /. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.
> [Sun Sep 01 19:38:22.058207 2019] [proxy:warn] [pid 11411] [client 88.161.215.60:65231] AH01144: No protocol handler was valid for the URL /error/500.html. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.
> [Sun Sep 01 19:38:22.226406 2019] [proxy:warn] [pid 11412] [client 88.161.215.60:65232] AH01144: No protocol handler was valid for the URL /favicon.ico. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule., referer: seafile.boschetti.pro/
> [Sun Sep 01 19:38:22.226691 2019] [proxy:warn] [pid 11412] [client 88.161.215.60:65232] AH01144: No protocol handler was valid for the URL /error/500.html. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule., referer: seafile.boschetti.pro/

what the problem?

thanks so much