The script works if you replace

const claimButton = '[data-test-selector="DropsCampaignInProgressRewardPresentation-claim-button"]';

with

const claimButton = '[class="ScCoreButton-sc-ocjdkq-0 ScCoreButtonPrimary-sc-ocjdkq-1 dNGoHt hdAxZi"]';

It might require further changes in the future, if Twitch decides to mess around with the code.

This fix stopped working but it was only a minor change so I updated the code:

const claimButton = '[class="ScCoreButton-sc-ocjdkq-0 ScCoreButtonPrimary-sc-ocjdkq-1 buUmIQ bxHedf"]';

They changed it again, here is the updated code:

const claimButton = '[class="ScCoreButton-sc-ocjdkq-0 ScCoreButtonPrimary-sc-ocjdkq-1 caieTg eHSNkH"]';

They changed it again, here is the updated code:

const claimButton = '[class="ScCoreButton-sc-ocjdkq-0 ScCoreButtonPrimary-sc-ocjdkq-1 ejeLlX eHSNkH"]';

They changed it again, here is the updated code:

const claimButton = '[class="ScCoreButton-sc-ocjdkq-0 cgOGyD"]';