This is a bug that has been reported in version 1.00.39 and earlier.

Workers at max level (level 10) have their ability cooldown at zero, but will not activate their abilities during levels. This is most common in Muradin and Teresa, but affects all Workers.

For now, there is no workaround this bug. We recommend that you invest in other upgrades in the shop that can help you reach your goals during levels, like furniture for bonus patrons/time, shop table upgrades so you can serve orders faster, and the like.

We're still working on this bug and will release a fix for it soon!