The Arduino library cannot be successfully installed.

I am trying to install a library called "pitsches.h" on Arduino IDE according to the textbook.
　Sketch→Include library→Install library in .ZIP format
If you select a ZIP library (pits.zip) in ,

The library named "pitsches" already exists.

The error appears."When I checked the pull-down menu that appears in the sketch→ library, ""pitches"" was not displayed."Even if I compile it as it is, I get the error "pitsches.h: No such file or directory", so I can't seem to install the library.By the way, the following is the full text of the error message when compiled:

 passive_buzzer:4:10:fatal error:pitches.h:No such file or directory
 # include "pitches.h"
          ^~~~~~~~~~~
compilation terminated.
exit status1
pits.h —No such file or directory

The results were the same whether "pitches.h" was enclosed in "" or ">" on the source code.

Extracting "pitches.zip" created a folder called "pitches", and only one file called "pitches.h" was created in it.When I tried to delete the "pitches" folder and compress only the "pitches.h" file in ZIP format, I got the error "The specified ZIP file does not contain a library."This does not appear to be a folder configuration issue for the original file.

"pitches.zip" is located in the "Document/Arduino/Libraries/" folder of the user folder.I don't remember having any special access restrictions on the files inside, but when I try to edit the files, Mac OS asks for the user'sTherefore,
　System Preferences → Security and Privacy → Full Disk Access
I tried adding Arduino in , but the situation didn't change.

Another "Document/Arduino/Libraries/" library file had the same results.

It's been a long time, but if you know how to install the library well with Arduino IDE, please give me some advice.

Environment:
Arduino: 1.8.13 (Mac OS X), Board: "Arduino Mega or Mega 2560, ATmega 2560 (Mega 2560)"