Error stopping OnlyOffice app with Community Doc Server

Error after removing and re-installing OnlyOffice connector app and CommunitydocumentServer.

Error when trying to connect (Client error: POST https://xxxx/nextcloud/apps/documentserver_community/coauthoring/CommandService.ashx resulted in a 405 Method Not Allowed response)

This happens when clicking the save button in the ONLYOFFICE settings. The document editing service address has been auto populated with https://xxx/nextcloud/apps/documentserver_community/
when the app was reinstalled but none of the options below the button are visible. Clicking save generates the error.

I removed the apps from the vanilla install on this server by clicking disable and then remove from each of the apps because of the bugs causing empty files, and then some days later decided to try something so re-installed them from appstore and now that happens.

NC 18.0.3
Ubuntu 18
PHP 7.4.4

The log in NC shows the following every time the button is clicked

Error	onlyoffice	CommandRequest on check error: Client error: `POST https://xxx/nextcloud/apps/documentserver_community/coauthoring/CommandService.ashx` resulted in a `405 Method Not Allowed` response		2020-04-11T13:13:17+0100