Problems installing v0.99? I have

19-09-19 16:21:02 ERROR (SyncWorker_8) [hassio.docker.interface] Can’t install homeassistant/qemux86-64-homeassistant:0.99.0 -> 404 Client Error: Not Found (“no such image: homeassistant/qemux86-64-homeassistant:0.99.0: No such image: homeassistant/qemux86-64-homeassistant:0.99.0”).
19-09-19 16:21:02 WARNING (MainThread) [hassio.homeassistant] Update Home Assistant image fails

Not sure, but this comes up when there’s not enough diskspace (> 1,3GB) for the update.

I had the same issue. Got it working by going to -> System. Then reload the Supervisor
After that I could update as normal