I wrote to them last week and the reply was as follows :Greetings from Hilton Athens!
With regards to your request, we regret to inform you that Executive Lounge will remain closed until further notice.
However, outdoor swimming pool operates daily 8AM to 8PM and we are offering our Hilton Honors Diamond members a complimentary voucher for drink (coffee/tea or wine or soft drink or beer) at Oasis Pool Bar & Grill.
Moreover, please note that since the restaurants are still closed, the breakfast is served in individual boxes either from Room Service or from Oasis Pool Bar & Grill.
Should you wish to make a booking, we will be happy to assist you.