Hi there,
I subscription Keil MDK v6 Professional Edition and I install the arem(mdk_541.exe) and C51( C51V961.EXE)
The Arm mdk license is actived but c51 license it still evaluation.
How to update C51 license from evaluation to full version
You need to generate a license for PK51 after you have installed the MDK professional license. You can read the details here:
developer.arm.com/.../Backwards-compatibility