Minecraft server icon can't be changed?

Unfortunately, I can't change the icon on my server. It has the correct dimensions and the correct name, but it still does not change. So far this has always worked without problems on my paper servers. Since paper currently doesn't work for me, I had to use a spigot server, is it because of that?

The icon must be 64x64 in size and be called server-icon.png. Then restart the server. If you already have all of this, check the size of the icon again.