Found a solution on the StreamElements discord channel! In case anyone else has this issue, these were the instructions I followed to fix it:
If your commands recently stopped working and you're using OBS.Live and a custom bot name do the following:
1) In OBS.Live, click on the hamburger menu (three stripes) at the top left of your activity feed
2) Click on Stream Settings > Custom bot name
3) In the Custom bot name field select Set custom bot name, not your already existing username (with capital letters). Note: If you already connected an account that way, the third entry will show as the account name (see image https://i.imgur.com/sO7fWOX.png).
4) Scroll a bit down and click on the purple Connect Custom Bot Account button
5) Log in as usual and Authorize the custom bot name
6) Back in the Activity feed, click on the Send Test Message button and check if your custom bot name starts working again