Could be that the hours have changed, but more likely that lounge closed early on that night due to a problem. Would be helpful if they had posted an apologetic sign.
When I called for clarification after arriving at a locked club that was the excuse the agent made - emergency closure. When I followed up yesterday, dissatisfied with Tuesday's interaction, the phone agent gave me the open times she was seeing which varied from a 7pm closing T-F to 530 and even 330 closing on Sunday.
Meanwhile the website still lists a static 6am-9pm club opening irrespective of day of week.