If you recorded just 1 Track, you are, likely, merging three MIDI Channel to Channel 1.

Cubase Elements Track Inspector has the MIDI In (MONTAGE-1 Port 1), the MIDI Out (MONTAGE-1 Port 1), and the OUT CH.

Set the Out Ch (just below the MIDI Out = “Any”
This will allow each of the three MIDI Channels you are Transmitting on to be sent back Out on the Channel they arrived on.

The MONTAGE Transmits each Part on its on MIDI Channel. (MIDI I/O Mode = Multi)
The 3 Parts of the “Imperial Grand” occupy Channels 1, 2 and 3.

If the Cubase MIDI Track’s Out Channel is set to “1”, you will only hear a partial piano (those Elements in Part 1) — Part 1 in the “Imperial Grand” piano is made up of the soft, medium soft, medium, and medium loud strike velocity Elements only.
In order to hear the other two Parts (which include the various hard strikes and the KeyOff Sound) you must allow the MIDI Track to Transmit all of the data it received.

When you played the MONTAGE you were transmitting on 3 Channels, you must playback all 3 Channels in order to hear the complete piano.

Extra Credit
A Cubase Elements MIDI Track will record all incoming MIDI Note/Controller events (which always include the Channel #)… the Out Channel setting will re-channelized the Out-going MIDI data, if you select a number 1-16.
When recording a multiple Channel source (like a Multi Part MONTAGE Performance, you will want to set that OUT CH so that it Outputs the actual MIDI Channel that the data came in on.

Setting this to “ANY” should fix your playback.

There are alternate methods to record Multi Part Performances — (by setting the “MIDI I/O Mode” parameter to suit what you are trying to accomplish)…

MIDI I/O mode = Multi - use this when you want to record each Part to its own MIDI channel. This is a requirement when wishing to document the MIDI events into the DAW. Quite naturally, where arpeggiated data is involved sending the data out on multiple channels is required when attempting to document the events.
MIDI I/O mode = Single - use this when performing on a multiple Part Performance where the Parts are used to create a single playable sound, like the "CFX Concert" or "Seattle Sections", and for viewing and editing a single stream of events makes the most sense.
MIDI I/O mode = Hybrid - use this when performing on a multiple Part Performance where the Parts are used to create a single playable sound, like “CFX Concert” or “Seattle Sections” for the ease of editing a single stream of events on one designated channel — this *hybrid* mode allows the other Parts to send and receive on their corresponding numbered MIDI Channel. (Literally, Hybrid is combination of Single+Multi. The KBD CTRL-linked Parts are addressed on one single channel; and all other Parts are addressed, as when Multi is selected, on their correspondingly numbered Channel.