The operating system may set your filesystems to Read-only when an error is detected with the filesystem or the disk.
When a filesystem is set to Read-Only, no data can be written and this can prevent services and other tasks from completing properly leading to a non-functioning server.
Note: Figuring out the reason for the error will be up to the System Administrator or the server owner as this is something that will not be related to the cPanel software.
For suggestions on locating the failure, you may refer to this article.
With that said, if no critical errors were found with your filesystem, you may attempt to remount it as Read-Write.
To do so simply run the following command:
mount -o remount,rw /
In this case "/" represents the filesystem that was set to Read-Only.