Can't display .jfif images in NextCloud

Hi. I am not able to see .jfif images in Nexcloud (web on PC and app on Phone the same).

If I put image directly to webserver. I can open image in browser with no problem. like https://server/image.jfif

But in nexcloud I see only grey icons (not assigned to any app) and when I click on it, it just allows to download, but it should open it in image viewer.

Is there any problem with my installation or this type of image is not supported by nexcloud?

I also tried to add mime type mapping to my configuration json file, but it did not help.

Any suggestions?