Casio piano seems to be frozen

"Casio CTK-501 Digital Keyboard Troubleshooting - iFixit" https://www.ifixit.com/Wiki/Casio_CTK-501_Digital_Keyboard_Troubleshooting

Help in the link, but you may have a sticky key on that reed instrument.

lots here
https://www.google.com/search?q=casio+ctk-574+factory+reset

A video here

It sounds like you may be experiencing issues with the sustain pedal on your Casio CDP-100 digital piano. The problem may not be with the pedal itself, but with the internal connections or circuitry of the piano.
If you're unable to factory reset the piano and it's not responding to the sustain pedal, it's likely that there is a problem with the main board. This is a complex issue that may require professional repair.
However, before giving up on it, you can try the following steps:

1. Check the connections: Make sure that all of the connections between the pedal, the piano, and the power supply are secure and that there is no damage to the cables.
2. Check the power supply: Make sure that the power supply is working properly and that the piano is receiving power.
3. Try to update the firmware: Check if there is a firmware update available for your piano on the Casio website. Updating the firmware may fix the problem.
4. Check the manual: Consult the piano's manual for troubleshooting steps, it may have some information that can help you.

If none of these steps work, it is likely that the problem is with the main board and it will need to be repaired by a professional technician. Unfortunately, this can be an expensive repair. Keep in mind that attempting to repair a digital piano can be dangerous if you're not familiar with the proper procedures and safety precautions.
It's important to keep in mind that the piano was second hand and you were aware of a problem with it and you have been given a lower price as a result. It is also important to note that buying second hand musical instruments may have hidden issues, which is why it's always advisable to inspect it thoroughly before buying it or to buy from a reputable seller who can give you a warranty.
Regenerate response

It is a known issue on this model.

https://www.google.com/search?q=%22casio+privia+px-100%22+pedal+not+working

Reset....but

https://www.fixya.com/support/t21517149-reset_privia_px_110_back_factory_setting

https://www.google.com/search?q=%22casio+privia+px-100%22+reset

..

Try this first with the piano off, run the control from stop to stop rapidly several times. The object is to clean off any dust deposits and shine the contacts inside the pot. If the pot is not damaged beyond repair, then this should fix it.

Pivots worn out or need lubricant. Make a warranty claim first.Otherwise, If out of warranty I would try to lubricate the hammer pivots myself. You will need "grease suitable for plastics".

I would unscrew the case to fix it only if it is out of warranty. Take it back to the dealer. Casio gives 3 years or 5 years warranty depending on the country.

Make sure you follow the steps of the procedure below exactly. Connecting incorrectly can make data
send and receive impossible.
1.
Turn off the digital piano and then start up
your computer.
• Do not start up the music software on your computer
yet

3.
Turn on the digital piano.
• If this is the first time yo
u are connecting the digital
piano to your computer, the driver software required
to send and receive data will be installed on your
computer automatically.
4.
Start up your computer's music software.
5.
Configure the music software settings to
select one of the following as the MIDI device.
CASIO USB-MIDI

Old reply so hopefully it's fixed. Dust or hair can get through the gaps and land on or near the contacts of the electronic key sensors. To be on the safe side (rather than doing a diy) take it in to the technicians. They'll have it fixed in a jiffy

Yep... Roland pedals are reversed, that is, normally closed contacts. Unlike some Yamaha keyboards, the Casio doesn't have an inversion function available. You have two choices to solve this: 1. Buy a pedal with the corect sense 2. Open the Roland pedal and MAYBE with a soldering iron you can move a wire to select a contact with the opposite sense.