Can't create sections

13" 2020 MacBook Pro with M1 chip. Mac OS Big Sur version 11.5.2. Safari browser version 14.1.2.

I click the sections button at the top and that causes text to appear that says “to add/modify sections, select measures in the score and click the section button that appears”. So I make my selection but then no section button appears.

Thanks to all and have a great day!