A team member has deployed a tiny change to the website. However, the change hides the [Checkout] button. Everything is fully functional, but the purchases in web store are decreasing in rapid rate. There are no errors, last deployment was green and telemetry is indicating the usual load. What's going on? The system needs to recover quickly to stop the bleeding of purchases and avoid the same situation in the future.
The first step is to investigate the negative feedback on social media (twitter) and see if it provides any specific information on the problem the site is facing.
Based on the tweets from customers and your manual testing of the site the team should be able to replicate the problem. As the first quickfix you could just re-deploy the previously deployed application code because to your knowledge that did not inhabit the same flaw.
Now that the site is behaving as usual and purchases are returning to normal, it is time to use the social media channel that gave you information about the problem to provide feedback to the customers that the problem has been resolved and purchases can continue. Make sure to use the #teamname hashtag when posting the tweets.