Thank you for your feedback!
I couldn’t reproduce issue with market. I checked market database, it does have “Clay” under listed resources to restock (with 50% ratio). Market updates it’s content once restock timer reaches zero. Then new values are calculated from current values of the warehouse. So if during restock warehouse had 0 clay, and then city produced 30 clay, market will have 0 clay to sell until next restock. If issue persist, you can try to open console (` key) and then enter restock_market to force restock of the market. Or you can try to wait for next restock timer to reach zero.
Taverns provides alternative ways to restore values, bypassing limits (starting from stone epoch) and reducing required time to wait (8/6/4 seconds for 100/105/110 energy compared to 20 seconds when sleeping from UI or 10 seconds using tent). This is why tavern’s actions have price.