Do you have anything plugged into the USB port?

Reset the Ace again, then reboot your controller's device and see if that helps.

Not much here:

https://support.sonos.com/en-us/article/update-your-sonos-ace

I’ve not had any update fails, but the process steps can be very slow. I often feel that it has failed, but if I wait a while longer it eventually gets done. There seem to be three main periods. During the first and last there will not be much communication with the user. In the middle period there will be percentage tics.

Thanks for your replies, solved, issue was I was trying to update when away from home via another wifi connection or 5g. Once on home WiFi and system showing in the Sonos app the update process started behaving immediately.