I seem to be experiencing the same vague "Attention Required" bug mentioned previously. I'm not sure why this is, but I managed to resolve it by commenting-out the "extends = two" from my theme definition. On a hunch, I tested this with the sample code for "Two" itself, which had the same bug, which was resolved this time by commenting-out "start_theme = two". Other themes seem to work fine, and as the "Two" theme seems a popular one, I'd guess the same step might get their projects functioning as well? Meaning either something changed with the theme, or how it's recognized by the program.