You say your URL is http://www.travelhappinesscompany.nl/ but the screenshot shows you asking for a certificate for the name travelhappinesscompany.nl which is different (lacks the www). To secure a site the certificate must be issued for the exact name of the site, not a different name. [ The certificate for plain travelhappinesscompany.nl was indeed issued on 8 February 2018 ]
You may also need to contact Dreamhost support (rather than Let’s Encrypt) if you run into problems using their control panel, since obviously Let’s Encrypt does not provide the Dreamhost hosting service you pay for.
Getting a certificate from Let's Encrypt only takes a couple of minutes and you already have one from 8th February that is covering your domains travelhappinesscompany.nl and www.travelhappinesscompany.nl and your site is already using it so you are done.
If you still receive that message on your Control Panel then you should talk to Dreamhost to know what is happening but as I said, your site is using the right cert.