Loading error jpg and png in external storage

Operating system and version: Ubuntu Core running on Raspberry pi 3b+

Hi, I need some help.
I installed the Nextcloud image from the Ubuntu store through this link, https://ubuntu.com/appliance/nextcloud/raspberry-pi.
Finished the installation , I proceeded to add an external storage precisely a 2 tb ssd that would boot when the raspberry starts.
I installed the plugin “external storage” I set the directory of the ssd /media/ssd , but when I try to upload an image to the external ssd I get the error “error loading image name.png” .