today I wanted to start printing those covers but failed to find an easy to use software. Therefore I started my VSCode with Sonnet and created a webapp in 2 hours to solve this problem.
Thanks for the report.
It should be fixed in v1.4.1
Because the tool it a Web-SPA it teands to be cached in your browser. Use Strg+R to relely refresh all site contents. Than it should work now.
But for the next time: Use Github issues to report bugs. Lets not spam this thread.