TripKey

Good luck. They've had all sorts of problems, and their prime distributor at Schiphol - Hertz - has ceased dealing with them.

If you put Tripkey into the search box you will find several fairly recent entries on the Forum (limit the search to the last 6 months of the Forum) which trace their difficulties (and those of their customers).

If you give us an idea where you are planning to go, we might be able to give you alternative options. Tripkey wont be an option.

Thanks for prompt responses Nigel and Floris. Floris, we have an apartment rented in Amsterdam for three weeks. Our plan is to see museums and points of interest in Amsterdam and also take day trips to other cities and towns, for example, Haarlem, The Hague, Delft, etc. TripKey seemed most convenient. How about OV chip card?

go with the OV chip card.
You can get them at the airport.
You just have to reload the card as you go along - less convenient than TripKey which we successfully used in April.

I've used the OV card on my last two trips to Amsterdam. Works fine, card is good for 5 years, but I've heard that getting a refund on your balance takes some effort. Just grab it at a machine in Schipol and throw 20EUR on it and you're good to go.

Depending on where you ars staying in Amsterdam, you might need even need public transport. Amsterdam has a very compact centre.

The anonymous ov-chipcard has a non refundable one time fee of EUR 7.50.

For train trips there is no price difference between an anonymous ov-chipcard and online tickets (via ns.nl/en or the NS app). Tickets bought at the station have an extra fee (for the disposable ov-chipcard) of 1 euro. The big advantage of an online train ticket is, is that checking in and out is not needed (or even possible). You only need the QR code to open the ticket barriers. At stations without barriers you just walk to your train.

Just grab it at a machine in Schipol and throw 20EUR on it and you're good to go.

Remember that at every check in when you use the train the balance must be (officially) at least EUR 20 (in practice a minimum balance of around EUR 15 is ok). For trams, metros and most buses there must be a positive balance on the card at check in.
Lets say you have a 20 euro balance on your card and you travel from Schiphol to Amsterdam, the remaining balance at Amsterdam Centraal will be EUR 15.70. Then you take a tram or bus. After that you wont be able to take a train with the remaining balance on the card without topping up (doesnt need to be EUR 20, you can top up more or less)

At the end of your trip you can get a refund of the remaining balance: https://www.ov-chipkaart.nl/applying-for-a-credit-refund/not-yet-expired-card.htm

By the way... OV-chipkaart is the name of the system. Tripkey, GVB multi day passes, Amsterdam and Region Travel Ticket and (non online) train tickets and others are also part of the ov-chipkaart system.

As there is no price cap when you use an anonymous ov-chipcard, check for deals also https://www.discoverholland.com (this is not a reseller, but part of NS)

Regular ticket prices can be found on ns.nl/en (trains only) and 9292.nl/en (all public transport)

I agree with the other posts--until Tripkey gets its act together, if you staying a long time in Amsterdam, get an OV-chipkaart. You'll be able to use it on buses, trams, and trains. Be sure to read the instructions carefully about initializing it for train travel and keeping at least 20 euros on your card when taking trips on trains. If you'd rather consider a Tripkey card, they sell it at a canal boat ticket office in central Amsterdam on a first-come, first-served basis. I'd call first to make sure they have cards in stock.

We've used ov-chipkaarts to travel around the Netherlands. After I had made our itinerary I used the NS website to see how much each round trip to different cities would cost us. I added on about 30 euros on top of that in case we wanted to use the tram a few times. When I bought our chipkaarts at the NS desk in Schiphol I had them load my total funds needed onto the cards - seems like it was about 150 Euro on each card. You just want to make sure you keep up with your card if you do that. If it gets gone then you would be out the monies on the card as anyone finding it could use it.
For the last two years we have gone to the train station on our last day and gotten refunded the balance on our cards. I can't remember if I read it or was told that they don't want to refund if your card balance is over 30 euros. You might check on that? Anyway, I planned carefully and we never had a problem getting refunds as it was always less than 30 euro. They ask you to fill out a paper with your name and address so they have a record of the refund and then they give you your money and the empty card to reuse on your next trip.

Have a superb visit!!!!!!

I can't remember if I read it or was told that they don't want to refund if your card balance is over 30 euros.

See: https://www.ov-chipkaart.nl/applying-for-a-credit-refund/not-yet-expired-card.htm
Over 30 euros a refund is not possible at the counter. You need to fill out a form and sent it in (with your card!). You also need an International Bank Account Number (IBAN).

Remember that even for your last train trip the minimum balance on the cards needs to be (officially) EUR 20 (in practice around 15 euros)