Samsung Galaxy A52 S5G won't open files

I installed the nextcloud app on the Samsung Galaxy A52 S5G from the play store. Now, when I try to open docx files, I constanly get an error, saying the file is ‘no longer offline available’ and I should turn on the ‘offline option’ in the contextmenu of the file. There is no option to do that in the contextmenu. Photos seem to work OK, excel files as well. It seems that the Samsung is looking for the broken files on the local storage, while the file in question isn’t there.

Anyone any idea?