Your CSS:
[data-toggle="collapse"].collapsed .fa:before {
content: "\f067"; /*plus*/
}
requires the row to have a class called "collapsed
" in order to show the plus. But you haven't given it that class:
<td data-toggle="collapse" data-target="#accordion1"
class="clickable" style="cursor:pointer">
If you use your browser's dev tools to look at the DOM, you will see that the Bootstrap library is adding that "collapsed
" class whenever you click the minus to collapse (beginning with the second click).
So of course you should start the element with that class already applied:
<td data-toggle="collapse" data-target="#accordion1"
class="clickable collapsed" style="cursor:pointer">