Ever since the release of Blender Octane v4.0 I've constantly had problems with the Denoiser causing server errors when rendering out animations. The problem got worse with each subsequent v4.0+ build. I checked drivers and uninstalled Octane/Blender with no improvement, untill I removed my Blender User Preferences, which forced me to re-check the Octane Addon in Blender's Addon panel, and that's when everything worked.
It turned out that somehow the Octane Addon being "automatically" checked and turned on by my user-preferences when Octane/Blender was installed and launched caused the Octane Addon not to register properly which led to the continued problems with the v4.0+ series.
*So note to anyone still having problems with server errors or problems with Denoiser creating crashes when rendering animation; after installing your v4.0+ of Octane/Blender after launch if the Octane Addon is checked (installed) then make sure to un-check it in Blenders Addons panel, save your preferences, close and restart Octane/Blender, then re-check the Octane/Blender Addon.
Please excuse my post if this has been mentioned in previous discussions.