The Play:1 requires a 2.4 wifi signal with the S1 App.  But even with the S2 App, I suggest trying the 2.4ghz frequency when these type of issues occur, can you turn off the 5 ghz signal and retry.

Edited: To correct an omission.

Both options are on, do I still have to turn off the 5ghz signal?

Yes just temporarily to connect the Play:1 than you can turn it on again.

Is this a new router or did it work on the same router before?

It worked on the same router before. Its not a new router

Also tried on my Android and Windows, same problem, same results. So it has to be my router/wifi

I also changed it to  bgn (instead using only gn), and tested separatly, no results.  still getting ‘cannot find the network or wrong password’(not possible, really my password is for 100% oke). I will contact my provider, maybe the have a solution.

No it doesn’t. The Play:1 can connect to either band.

​@Esje2424 - The Play:1 doesn’t support WPA3 security so check that you have allowed WPA2 in your router settings.

Also see this link for supported Wi-Fi modes :

https://support.sonos.com/en-gb/article/supported-wifi-modes-and-security-standards-for-sonos-products

Sort of. ​@Esje2424 are you using the S1 or S2 app? The S1 only supports 2.4, so I recommend a user connect to that frequency when stability issues occur.

S1 and WPA2.

Thanks all for helping&tips. Still working on it.

Temporarily connect it by ethernet to your router to complete the setup.