Cause: Arm Compiler 5 requires a valid license. The evaluation license for MDK 5.36 is separate from newer versions.
Solution:
Keil v5 represents a bridge: it kept traditional ARMCC optimizations and vendor integrations that long-term embedded teams trusted, while later toolchains shifted toward upstream Clang/LLVM-based compilers and modern toolchain practices. Teams migrating from v5 often weigh compatibility, certification history, and available device support when choosing a newer toolchain. keil arm compiler version 5 download
Open the Build Output window. You should see something like: Cause: Arm Compiler 5 requires a valid license
*** Using Compiler 'V5.06 update 7 (build 960)', folder: 'C:\Keil_v5\ARM\ARMCC\bin'
That confirms success.
Cause: Your license is for MDK-Lite (32KB) or AC6-only.
Solution: Purchase an MDK Professional upgrade or use the evaluation license. That confirms success