In file included from H:\Arduino\21-3-12_MainTransmitterReceiver\21-3-12_MainTransmitterReceiver.ino:4:0:
C:\Users\user\Documents\Arduino\libraries\ESPAsyncWebServer\src/ESPAsyncWebServer.h:33:22: fatal error: AsyncTCP.h: No such file or directory
compilation terminated.
exit status 1
Error compiling for board ESP32 Dev Module.
In file included from C:\Users\user\Documents\Arduino\21-3-12_MainTransmitterReceiver\21-3-12_MainTransmitterReceiver.ino:4:0:
C:\Users\user\Documents\Arduino\libraries\ESPAsyncWebServer\src/ESPAsyncWebServer.h:33:22: fatal error: AsyncTCP.h: No such file or directory
compilation terminated.
exit status 1
Error compiling for board ESP32 Dev Module.
In file included from C:\Users\user\Documents\Arduino\21-3-12_MainTransmitterReceiver\21-3-12_MainTransmitterReceiver.ino:4:0:
C:\Users\user\Documents\Arduino\libraries\ESPAsyncWebServer\src/ESPAsyncWebServer.h:33:22: fatal error: AsyncTCP.h: No such file or directory
compilation terminated.
exit status 1
Error compiling for board ESP32 Dev Module.
21-3-12_MainTransmitterReceiver:4:31: fatal error: ESPAsyncWebServer.h: No such file or directory
compilation terminated.
exit status 1
ESPAsyncWebServer.h: No such file or directory
In file included from C:\Users\user\Documents\Arduino\21-3-12_MainTransmitterReceiver\21-3-12_MainTransmitterReceiver.ino:4:0:
Your .ino file is in a folder in C:\Users\user\Documents\Arduino\ so that is your sketchbook directory. What does File/Preferences show as your sketchbook directory ?