The single bracket notation is for [inline labels][1], which are like tooltip comments that appear when you hover your cursor over the roll output. When numeric characters are inside the inline label brackets, they are usually rendered as regular text, and are not added to the dice roll.

From your question, it seems like you're using the Starfinder template for Roll20 character sheets. There should be an area like this:

[![enter image description here][2]][2]

To add the +1 as a bonus to the roll, you need the numeric parts to be outside the inline label. For example, you could fill in the text as "`+1 [insight]`":

[![enter image description here][3]][3]

This notation should add the +1 to your attack rolls. When you hover the cursor over your attack rolls in the chat area, the text "insight" should be visible in the equation.


  [1]: https://wiki.roll20.net/Dice_Reference#Inline_Labels
  [2]: https://i.sstatic.net/QpF5c.png
  [3]: https://i.sstatic.net/QGWui.png