css edits not showing in dreamweaver

I'm surprised they told you to go backwards. Can you try going back to 21.6 and upgrade to OS 15.7.1? But regardless the problem does not sound related to DW but more to your code. Have you tried validating your code? https://validator.w3.org/

Upload the problem page to your server and post the URL here for us to look at.

My guess without seeing anything is that you're attempting to change the wrong selector and nothing is happening. 

Moving elements around in an outdated Template is often more trouble than it's worth.  It might be simpler to start over from scratch. 

Make a pencil & paper sketch of where you want things to display on mobile, tablet and desktop.

Use that as your prototype for creating a mobile-first layout with Bootstrap. 

Code questions require you to give the code, otherwise it's all guesses.

Copy and paste your entire css code into a forum response (DO NOT use email replies, code won't come through).

Next, paste the entire html code of the page in question.

Be as descriptive as possible as to which element you want to change and how you want it changed. One of the contributors here will be able to get you going in no time.