Recording works but no playback sound from Fantom-X8 in Logic Pro

Is this an Audio recording or a Midi recording? Two different types of recording. Sounds like you're recording Audio/Sound.

Audio (sound):

Go to Logic's Preferences/Audio and make sure the Scarlett is selected for both Input and Output. You have speakers or headphones plugged into the Scarlett and the output level on the Scarlett halfway up.

MIDI (Data):

Uses two Midi cables Midi Out of the Fantom to Midi In on the Scarlett, Midi Out on the Scarlett to Midi In on Fantom. MIDI channels must match.

Did you download and install the Mac software for that Fantom X8 from Roland?

Do you see your Fantom X8 in the Mac Audio MIDI Setup—both Input and Output?

Do you see it in Logic Pro Settings, Control Surfaces, MIDI Controllers tab?

I connect my Roland devices directly to my Mac via USB and don't use my audio interface at all for my MIDI controllers. According to my Search results and the Fantom X8 manual, you can connect directly to your Mac, via USB once you have the Roland software installed.

Take you Fantom Left and Right audio outputs and plug then into the Scarlett audio inputs, you should now hear the Fantom's piano.

"However, when I play the track back, the Fantom’s internal piano sound is not heard. I would like to record and play back using the Fantom’s built-in piano sound.

When I switch the instrument to a Logic software instrument (e.g. Logic piano), the sound is heard without any problems. But when I switch back to the Scarlett output, I can see the MIDI signal moving, yet no sound comes from the Fantom.

Could this be because the Fantom X8 is too old to connect properly with Logic?"

ADDENDUM: To get the Roland internal piano sound recorded, since it's not a Logic instrument, an audio recording is likely the only way to record that internal piano sound.

1. See if your Fantom X8 is an audio device, not just a MIDI controller.
2. If it is an audio device, can it record audio via USB. At a quick glance, I don't the answer in the manual.
3. Your Fantom X8 does have 1/4" outputs, which I would use to record the internal piano sound.

Here's the answer I found for you.

No, the Roland Fantom-X8 cannot record audio directly via its USB port. Its USB connection is for data transfer, such as loading samples, or for MIDI and audio storage functions, not for direct audio recording into a computer. To record audio from the Fantom-X8, you must connect its analog outputs (L/R 1/4" jacks) to a computer's audio input or an external audio interface. 

How to record audio from the Fantom-X8

• Connect to an audio interface: The recommended method is to connect the Fantom-X8's "A MIX" L/R 1/4" outputs to your computer's audio interface inputs.

I found a video that tells you how to record audio with your Fantom X8.

https://youtu.be/1sNQPUXR0rk?si=5k70vGqglY-TV9FV

Since the Fantom has Audio Inputs there is more than one way you can configure your system.

From what I understand you can not record into the usb from the fantom x8.