Did you try a power cycle?

Might be time to call Support. 

How did you solve this?

My Sonos play 5 second gen has a failed wi fi card ? What does that mean and how did it happen ?

Depends on the extent of the failure. Who told you it was a WiFi card failure? If it is indeed just the WiFi, you could wire it directly with an Ethernet cable. If it’s more serious than just WiFi, that may not work, though. You may want to call Sonos Support directly to discuss it. In some situations, they may offer you (or you may be eligible for) an upgrade discount. 

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Even the PLAY:5 gen 2 is getting fairly long in the tooth, although my stereo pair are working fine. I’ve been holding off on updating them, but may need to change that, as the Five is supposed to sound better, and is certainly newer electronics inside.

It works with an Ethernet cable but it’s not possible to use that full time as the router is too far from the room I have my system set up in,they confirmed it’s the wi fi card,not working how can this happen all of a sudden when yesterday it was all working fine ?

Electronic devices fail on their own schedule, it could have just been time. Could have been a small surge that nudged it over to failure. Possibly oxidation/crud buildup on a critical junction.

Unless electronics repair is a hobby and you dig in for fun you are usually going to spend more than the device is worth finding the problem, then more repairing it IF you can get the parts.