calibre, version 8.16.2
ERROR: KFX conversion failed: <p><b>Cannot convert The Hidden Staircase</b><br/><br/><b>Conversion error:</b> The source file C:\Users\xyz\AppData\Local\Temp\6ace7578-353c-476f-bc76-5b9bbd9f9db4\cTemp\conv_temp\preprocessed\0_1_67f8 94a6894a25c2_7-titlepage.xhtml cannot be read.</p>
I updated to the latest plugin. I've converted many books over the years and just now it keeps failing.