Running Fedora 23 KDE Spin almost default set-up.

When I connect an external disk (part encrypted and part normal), in the device notifier, it shows as two disks.

On clicking the normal partition, it loads properly in dolphin

On clicking the encrpyted part, it asks for a password. On entering the password, nothing happens. It continues to show as encrypted disk in dolphin.

If I try to mount it again, it produces an error.

What is happening? How do I load this?

For an encrypted disk, many things can go wrong with the result that the disk does not get mounted.
You should probably try to narrow the problem down by trying to break the mount process in steps which
are not performed within dolphin so that you can access easily possible error messages. The following is for a
debian system, but Fedora is probably similar.

1. How is the disk encrypted - do you have all tools installed which are necessary for decryption?
2. Assuming for example a Luks emcrypted partition you can 'map' the encrypted partition to a regular block device
by doing as root
# cryptsetup luksOpen /dev/sdbX any_name
where sdbX is the kernel device name of the encrypted partition and any_name the name of the created block device.
Below /dev/mapper you will find 'any_name' .
3. Now try to mount this device, e.g. on /mnt
# mount /dev/mapper/any_name /mnt
If this does not work, note the error messages of 'mount', also check dmesg to see if the partition type (the de-crypted type)
was identified correctly and that the partition is error-free. You may have to
# fsck /dev/mapper/any_name
if the partition is inconsistent. Then retry the mount.

Fedora probably has a path like /media/<your user>/<some device ID> where removable media typically show up.
If this path exists, try to lower permissions (I recently had an issue with the intermediate /media/<your user> belonging to
root, when I changed the owner to my own <your_user> in your case, things worked normally.

The error on the second mount attempt could be due to the device being mapped, but not mounted correctly. Also check /etc/mtab, where
mount reports all 'mount'ed partitions.

Good luck.