How do I set breakpoints in the extension for debugging？

I suspected that the manifestURL file had failed to download, but a review of the console logs reveals that the download is complete. backgroundassets.user Process logs: Download did finish: BAManifestDownload (0x90ce258e0) - com.my.bundleid.Manifest-60F3F3DF-3B06-4031-A926-E658055EF83C Download did finish done.