Document, opend with onlyoffice readonly

I can open the existing document (XLS), but it is in readonly mode. Did I miss something in the settings?
NC 18.0.1
OnlyOffice APP 4.1.4
CommunityDocumentServer APP 0.1.5

OO does not do xls, best to convert to xlsx by right clicking the file and choose to convert. You can allow read write for xls in the settings but this is not recommended.

Thanks, but I allowed already “The default application for opening the format” xls and it is not possible to do it here “Open the file for editing (due to format restrictions, the data might be lost when saving to the formats from the list below)”.
For me it is not the best practice, that no information popped up, like "Edditing this fileformat is not supported by this OnlyOffice Version, please convert it …)
But anyway, the solution is given with your answer, thanks!

Agreed they need to add a message like you suggest, I get confused every once in a while even though I know about it.