tickets for Hotel de la Marine

The website says:
"Online ticketing is temporarily unavailable. Tickets can be purchased on site. We apologize for any inconvenience this may cause."

I'd check back later or, if already in Paris, buy tickets there. This is the page of rates for individuals and groups:
https://www.hotel-de-la-marine.paris/en/visit/practical-information

The entire Centres de Monuments Nationaux ticketing system, which manages bookings for Hotel de la Marine and many other sites in France including Sainte-Chapelle and the Towers of Notre Dame, has been down for several days.

As Kate said, check back or buy your tickets on site. My experience last April was that advance booking was not necessary.

The audio guide provides a wonderful tour of the Hotel de la Marine. Enjoy your visit.

I was there two weeks ago.
I arrived at around 11:00 with no ticket and was able to buy one for 12:00.
I just went for a walk then came back for my visit.
Get there earlier.

I'll just add that this is a very cool venue! I loved the audioguide which was from the POV of different people who lived and worked in the palace. I really enjoyed the visit last Fall.

I had the Passions Monument Subscription that Jeanm often suggests. Depending on how long you will be there and what else you plan to see it might work for you as well. It, however, is purchased thru the monuments site that is currently down.

The first time we tried to get tickets for Hotel de La Marine, it was sold out for several days so definitely get them ahead. Right now the ticketing systems for several sites are down -- so just try every few days -- surely they will get it fixed. I need to get tickets to take my grandson up the Notre Dame Tower and that site is also unavailable.

Thanks for the advice. I went to the online site for ticket prices and it said:
Intendant's Apartments and Salons & Loggia
17 €
Al Thani Collection and Salons & Loggia
13 €
Salons & loggia tour (inter-exhibition period)
9 €

Which ones are best to see? All of them? we are on the older side and do not like to do a lot of stairs so that is a consideration.

Get the ticket for the whole place -- the most expensive one -- the most interesting rooms are the private rooms IMHO rather than the public rooms on the shorter visit. I don't remember stairs but I could remember wrong. There is a good view from the loggia of the huge plaza at Concorde

There are stairs involved, including the Grand Staircase.

The website indicates there is an elevator. Speak to the attendant for access.

There is an elevator, you just have to ask.
The staff are helpful.

FYI the ticketing website is currently up and running.