dock not showing up when located in left side

Hi kwon176,

Thank you for participating in the Apple Support Communities. We understand the Dock does not show when it's locked on the left side. We recommend testing to see if the issue occurs in safe mode. This can help isolate the issue. Here's how: Start up your Mac in safe mode.

"Starting up your Mac in safe mode can help you identify whether issues you’re experiencing are caused by software that loads as your Mac starts up.

Before you begin

To start up your Mac in safe mode, you need to know what type of Mac you have.

1. On your Mac, choose Apple menu  > About This Mac.
2. Look at the information in the window to determine what type of Mac you have:

• If you see an item labeled Chip, followed by the name of the chip, you have a Mac with Apple silicon.
• If you see an item labeled Processor, followed by the name of an Intel processor, you have an Intel-based Mac.

3. Use the corresponding set of instructions below to start up your Mac in safe mode.

Start up your Mac with Apple silicon in safe mode

1. On your Mac, choose Apple menu  > Shut Down.
2. Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.
3. Press and hold the power button on your Mac until “Loading startup options” appears.
4. Select a volume.
5. Press and hold the Shift key, then click Continue in Safe Mode.
6. The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar.

Start up your Intel-based Mac in safe mode

1. Turn on or restart your Mac, then immediately press and hold the Shift key until you see the login window.
2. Log in to your Mac.
3. You might be asked to log in again.
4. On either the first or second login window, you should see “Safe Boot” in the menu bar.

Verify your Mac started up in safe mode

If you’re unsure whether your Mac started up in safe mode, you can use the System Information app to check the mode.

1. On your Mac, press and hold the Option key, then choose Apple menu  > System Information.
2. In the System Information app, select Software in the sidebar.
3. In the System Software Overview, look at the value listed next to the item labeled Boot Mode.

• Safe: The Mac is using safe mode.
• Normal: The Mac is not using safe mode.

For more information about using safe mode, see the Apple Support article How to use safe mode on your Mac."

We also recommend making sure you have the latest version of macOS: Update macOS on Mac.

Take care.

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Glad to have helped. 👍