I was trying to make a new list with the app and and raithos.github.io it seems

Spare Parts Canisters is greyed out.

Is this a mistake or is there a new change?

Nope nevermind figured it out lol

For context, Spare Parts Canisters requires an equipped Astromech.

Reference! (Note the "astromech equipped" requirement at the bottom left, as @theBitterFig mentioned)

YASB 2.0 doesn't show what the upgrade restrictions are when you're making a squad... you have to figure out why you can't equip a certain upgrade on your own. It's one of the few shortcomings of what is otherwise a very clean and highly-functional squad builder.