Why are some ISO files not mountable via Supermicro iKVM Viewer

I am using a Supermicro server, and its ipmi firmware has a so called "Virtual Media" function. It allows you to mount an ISO file, which is then presented to server as a USB CD-ROM.

I cannot understand why some of the ISO files are not mountable. When I choose an ISO file in Virtual Storage menu, and then click Plug in button, I got message:

Device1: Can not open ISO Image File

But some other ISO files are able to be mounted correctly with the message:

Device1: VM Plug-In OK!!

I thought that the ISO file size could be a problem, but seems it is not.

Edit: there is a similar question, but in that case the cause was firewall.

Solution 1:

It is the problem of java iKVM Viewer. It for some reason requires a write permission to your iso file. If it is missing, then mounting fails.

I have accidentally found mentioning of such requirement from the very end of this article.

Solution 2:

Also, I noticed on the iso's that would not mount, I was not the owner like the other files. Once I changed ownership I was able to mount them.