Docker nextcloud 400 Bad Request

Hey there,

I have problem in connecting my nextcloud server to onlyoffice server.

In ONLYOFFICE setting in nextcloud i got this error message:
Error when trying to connect (Error occurred in the document service: Error while downloading the document file to be converted.)

I tried to check connection between servers with wget command.
in nextcloud server i can call onlyoffice
but in onlyoffice server i can not call nextcloud server with wget command, this is the command result:

# wget nextcloud
--2018-09-13 12:27:23--  http://nextcloud/
Resolving nextcloud(nextcloud)...
Connecting to nextcloud(nextcloud)||:80... connected.
HTTP request sent, awaiting response... 400 Bad Request

i have tried using other server to call nextcloud using wget with the same error message.

i put those server behind nginx proxy, and i can access both it from outer networks via that’s nginx

i have tried to rebuild the docker image, but the error still there.
Do anybody knew what’s the problem with my nextcloud server?

Any help would be appreciated.