Embedding NotoSansCJK font subset results in all texts invisible in output PDF document

[BrookeTsui]

I'm using TCPDF version 6.3.2

I used tcpdf_addfont.php -b -i NotoSansCJKtc-Regular.ttf to create notosanscjktc.ctg.z, notosanscjktc.php and notosanscjktc.z in the font directory.

With SetFont('notosanscjktc',$style,$size) for embedding font subset, the output PDF document has all texts INVISIBLE.

With SetFont('notosanscjktc',$style,$size,'',false) for embedding the whole font, the output PDF document becomes NORMAL i.e. all texts VISIBLE.