The good news is it didn’t delete your project when the build failed. (that has been reported to happen) I’ve lost it in the open screen but the project remained in the workspace.
If this is a Manifest error it is because you have a number as the first character in a segment.
See this TOPIC
It must have at least two segments (one or more dots).
Each segment must start with a letter.
All characters must be alphanumeric or an underscore [a-zA-Z0-9_].
When it fails take a screen shot of the error report and post that.
Ron