Maybe you are using a buggy version, see also NethServer-Onlyoffice module upgrade to make the latest Onlyoffice versions work - #4 by mrmarkuz
Please try
yum -y reinstall https://mrmarkuz.dynu.net/mirror/devtest/nethserver-onlyoffice-0.0.3-1.ns7.noarch.rpm
If it still doesn’t work, let’s check the onlyoffice configuration:
config show fw_onlyoffice
occ config:app:get onlyoffice DocumentServerUrl