I just shortened the length of my animation by selecting all the keyframes in the dopesheet and scaling them down (as per advice on a thread here on stack exchange) and now my animation won't play. If I continuously hit spacebar it scrolls through a frame at a time and it will play backwards not forwards. Also, if I delete any key frame then ctrl+alt delete, the animation plays fine until I stop it then it won't start again and it's back to the same. Any help with this greatly appreciated!
I've checked start stop in output properties and they are the same as timeline. And this happens in Eevee and cycles. I've tried earlier autosaves (even before this started) and it's the same problem.
The pic shows the fps constantly cycling round itself on a single frame in forwards play
Ok I think I sorted it! The usb power for my sound card had decided to turn off but I wasn't to know as the volume was down at the time so thought it was something more complex! Turned the interface off and on again and sorted it! Hope this solution helps anyone else with the same or similar issue
In may case "Play animation" button played one frame forward and played normally backward. There was no sound. What I did to fix the issue I deselected the audio device (it defaulted to "PulseAudio") by setting it to "None".
At that point blender froze up for several minutes but finally it started again accepting input. Again I set it to "PulseAudio" and playback started working properly.