Only Office Error: Server connection lost. The document cannot be edited right now

After hosting of Only Office some time users can get the error “Server connection lost. The document cannot be edited right now“.? To resolve this error we can remove 2 values from the web.config key of the Document Server setup.

By default values:
<add key=”editor.settings.coauthoring.url” value=”/coauthoring” />
<add key=”editor.settings.spellchecker.url” value=”/spellchecker” />

Remove values like that:
<add key=”editor.settings.coauthoring.url” value=”” />
<add key=”editor.settings.spellchecker.url” value=”” />

and reset the IIS.