The Play:5 and the Five use an industry standard connector. Any 3.5 mm stereo plug should fit. 

It would be hard to find a more standard plug than a 3.5mm plug.

A picture of your cable “not fitting” would help.

I too would have thought any 3.5mm TRS adapter would fit - they’re pretty much standard.. but perhaps see this link about TRRS adapters:

https://www.eksa.net/blogs/news/trs-and-trrs-the-differences-that-you-need-to-know-about

It ‘clicks’ into place when pushed in…

Hope that assists.

Is it there now? You may need to refresh the page. It’s alongside a tape measure.

Occasionally, I must push uncomfortably hard in order to fully seat a 3.5mm plug. If the plug is the standard length shown above, don’t be afraid to fully seat the plug.

On occasion I have seen a few modular power supplies that seem to be using a 3.5mm plug, but is is longer than standard and may not fully seat in its socket. This is not your situation.

Sometimes a slight rotation as it bottoms out will ease it past the internal connections.

no out put . The app recognize the 3.5

How Hard do you have to push it in?

This is the adapter from my Sonos Five and it goes in to the hilt (about 12/13mm). See attached.

Thank you Ken, cannot see image can you reload thanks