cannot increase dock icons size

Try to restart your mac. If this will not help you may try restarting your Mac in Safe mode:

- Shut down your Mac

- Wait until your computer turns off and after that press the Power button

- Right after you hear the startup tone, press and hold the Shift key

- Release the Shift key when you see a grey Apple sign and the progress bar below this sign

Restart your mac.

If this will not help try to reset SMC: Resetting the System Management Controller (SMC) on your Mac - Apple Support

Back up all data before continuing.

Please triple-click anywhere in the line below on this page to select it:

defaults delete com.apple.dock size-immutable && killall Dock

Copy the selected text to the Clipboard by pressing the key combination command-C.

Launch the built-in Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

Paste into the Terminal window by pressing the key combination command-V. I've tested these instructions only with the Safari web browser. If you use another browser, you may have to press the return key after pasting.

Wait for a new line ending in a dollar sign ($) to appear below what you entered. You can then quit Terminal. Test.

If applicable, get rid of the third-party "utility" that you used to hack the Dock settings.