Welcome to the Asana Community Forum @anon34732901!
When it suddenly wasn‘t working anymore no change was made to the project correct?
And you have full access to the project like before?
Have you tried rebuilding the chart again to see whether the same thing happens?
I also recommend checking the troubleshooting steps such as logging out and in again, clearing cache, etc and if nothing helps contact support as they have more tools looking into your account directly etc to figure out why this is happening.