[Plugin: Widget Logic] After updated,. widget broken,.

hard to say. does it work if you simply use ‘false’ or ‘true’. How about in the default theme?

hang on, is_post_author isn’t a core wordpress condtional tag. you can make one using

https://codex.www.ads-software.com/Function_Reference/get_the_author

eg is_single() && (“X”==get_the_author())

might work