How To justify text of specific blocks on squarespace 7.1

im trying to justify writing of specific blocks nothing seems to work (im aware its not ideal but its what my client wants) i've scoured all the youtube videos and guides i can find. None of the solutions have managed to work. I have the squarespace block id identifier chrome extension. None of the code i try seems to work on my website. I can copy the code to justify the whole website. But not the specific text blocks. Does anyone have the working code for this?

(Here's one of the example codes that didn't work) 

Use this code to justify a specific text block

#blockidnumber {
 text-align: justify;
}

This should be pretty straightforward. Can you share the website and password if it's private?

Justify won't work on All browsers/mobile devices

it will create spacing problem on some mobiles

If you still want, try this code

#block-id * {
	text-align: justify !important;
}

Use this tool to find block id. https://chrome.google.com/webstore/detail/squarespace-id-finder/igjamfnifnkmecjidfbdipieoaeghcff?hl=en