ONLYOFFICE and Nextcloud 27 no function

i have two nextloud 27 installations. after update from 26 ONLYOFFICE dos not work.
the settings for ONLYOFFICE ar not shown und office files will download after klick

There’s already an issue filed on Github:

Under the administration page, overview then the version heading… is your installed version listed as an rc (release candidate)? If so, you need to upgrade to the new 27.0 release otherwise you won’t be able to upgrade to OnlyOffice 8.0 successfully.