Can´t mount encrypted external hdd after encryption was interrupted
A reboot usually un-pauses conversion, so I would try that first. Consider storing the passphrase in your keychain (even if temporarily) so that it mounts when you log in and gets going on conversion after the restart. 

You are doing it perfectly - looking at diskutil cs list and checking the "Conversion Progress" and "Conversion Status" fields.

A restart might be overkill, you could try:

diskutil eject disk3
diskutil eject disk2


Once both the logical and physical volumes are detached, you could disconnect physically the drive and then wait a slow count or two and then reconnect.