Error: Could not find executable for ARMC6

I am working NuMaker-PFM-M2351. I have installed mbed-client accoring to the official page on Ubuntu 18.04.
When I try to compile a blink example code, I get the following error:

[mbed] Working path "/home/pramod/NuMaker-mbed-TZ-nonsecure-example" (program)
[mbed] WARNING: Missing Python modules were not auto-installed.
   The Mbed OS tools in this program require the following Python modules: hidapi, pywin32
   You can install all missing modules by running "pip install -r requirements.txt" in "/home/pramod/NuMaker-mbed-TZ-nonsecure-example/mbed-os"
   On Posix systems (Linux, etc) you might have to switch to superuser account or use "sudo"
[mbed] Exec "/usr/bin/python -u /home/pramod/NuMaker-mbed-TZ-nonsecure-example/mbed-os/tools/ -t ARMC6 -m NUMAKER_PFM_M2351 --source . --build ./BUILD/NUMAKER_PFM_M2351/ARMC6 -v" in "/home/pramod/NuMaker-mbed-TZ-nonsecure-example"
Could not find executable for ARMC6.
Currently set search path: /home/pramod/ARM_Compiler_5.06u6/
[mbed] ERROR: "/usr/bin/python" returned error.
   Code: 2
   Path: "/home/pramod/NuMaker-mbed-TZ-nonsecure-example"
   Command: "/usr/bin/python -u /home/pramod/NuMaker-mbed-TZ-nonsecure-example/mbed-os/tools/ -t ARMC6 -m NUMAKER_PFM_M2351 --source . --build ./BUILD/NUMAKER_PFM_M2351/ARMC6 -v"
   Tip: You could retry the last command with "-v" flag for verbose output

When I try to compile for the device K64F with toolchain as ARM, it successfully compiles but does not work for NUMAKER_PFM_M2351
I’ve only been working with mbed-cli for a couple weeks, so I apologize in advance if I haven’t included enough information.