Images does not appear as thumbnales and are not viewable without downloading

Dear Nextcloud community, I want to share pictures with my family and used a public link for a folder. I tried to upload files from several mobile phones .Unfortunately I am not able to see the images in any of the Nextcloud apps unless I download them and open them in some local app. Does anyone know what might be wrong? However files that are added from a desktop computer are visible in the folder when I open from a browser. But the ones that are added from my mobile phone have to be downloaded first.

I want all the photos to appear in the folder but when I click on them i get the message “error loading”.
I use the Nextcloud Dev app for Android version 20200610 I think I am on the latest Nextcloud version, Debian Buster. I am on a community server so I have no admin rights. But I thought I check here before I bother our admin.
All the best

Dear Community this problem persists I get the same error loading when trying to view the image in any web browser. I am thus not able to share images with other internal and external users. Locally though within the webdav desktop sync client both in debian and OSX I can view the image but not the thumbnail. I know that the above explanation was not very detailed. What more info should I provide?

I now tried another Nextcloud instance that is 21.0.1 and uploading and sharing photo folders and contents + thumbnales worked without problems.
The instance not working is on 20.0.9.