Here are some issues that may be common:

"Permission denied" error when running on Linux

Ensure that md2blog is executable (if not: chmod +x md2blog).

"Developer cannot be verified" error on macOS

Pre-built binaries for md2blog are not signed (currently, this is not possible with Deno), so macOS may refuse to run md2blog with an error similar to "'md2blog' cannot be opened because the developer cannot be verified". Options to get around this:

• Ignore the error: "System Preferences" > "Security & Privacy" > "General" > "Allow Anyway" (as noted here)
• Install Deno and then use deno install to install md2blog as a script

"content" not found error

By default, md2blog reads from an input directory named "content". You can change the input directory using command line options (namely --input).

"site.json" not found error

md2blog reads the site title (and optional description/URL/theme) from content/site.json. See the quick start for more details.

My site built fine before, but now it's not building anything

Check the console output to see if there is a message about broken relative links, e.g.:

Error: The site has broken relative links:

From "posts/faq/common-problems.html" to "../../quick-start.html#Setup"

If you're running with --clean and there is a broken relative link, the build is aborted after the output directory is cleaned, so the output directory will be empty. Just fix the broken link and rebuild.

I hit some other error not listed here

Consult the FAQ entry on general support info. It contains links to the discussion board and issue tracker.