Other svg files are visible both in the file manager and on the desktop. I am confused.

Does it display in a browser?

No, it doesn't display in any of the browsers I have (Firefox, Brave and Edge). Neither in the image viewers nor in Gimp when I import it. Only in Inkscape and Libre Office Draw.

Feel free to share it, if you would like us to take a look.

This thread looks like it hasn't been active in a while, but I have the same issue.

Everything appears correctly in Inkscape, but when I open the file in my web browser (or any other app, like PowerPoint), the clouds/sky in 2nd-4th panels are invisible. The first panel is a raster image, so it shows up fine. I've tried many different solutions, from exporting as a plain svg, grouping/ungrouping objects, and nothing seems to work. Any advice is greatly appreciated!

Click on one of the problem panels, ungroup, then look down at the taskbar at the bottom of the screen.It says that the blue sky object is clipped. Click it once to select, then right click and select Release Clip from the menu. Delete the black square (clipping path object) to leave the blue gradient underneath, then save. This worked for me in Firefox.