Nextcloud15 can not use onlyoffice?

The version of software I installed in the past is 14.
And used onlyoffice to read doc files.
Recently, I found that the software has been upgraded.The Software version is 15,and found that the onlyoffice was available.
How can I recover?

Unfortunately I didn’t understand what you want to do. If you want to open a file with a specific extension by OnlyOffice you should check your web browser or system settings which application
is associated with the relevant file extensions.