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ARMCLANG: Error: Failed to checkout a license (ARM Compiler 6 + Win10)

Information in this knowledgebase article applies to:

  • MDK V5
  • Arm Compiler 6
  • Windows 10 "April 2018 Update", known as version 1803, Redstone 4, or RS4
  • Keil Single User License and Keil Floating License


I have installed MDK V5 and my Operating System is Windows 10, version 1803. My MDK-installation is registered as a Single User License.

After updating my Windows OS to version 1803, building my project with Arm Compiler 6 results in error messages, i.e.:

*** Using Compiler 'V6. ', folder: 'C:\Keil_v5\ARM\ARMCLANG\Bin'
Rebuild target
ArmClang.exe: error: Failed to check out a license.Keil Licensing error: No TOOLS.ini file found
ArmClang.exe: note: Check that your license details are correct in the License Management dialog of MDK. Additional information is available at:
If you need further help, provide this complete error report to your supplier or
- Product location: C:\Apps\Keil\ARM\sw\mappings
- Toolchain location: C:\Apps\Keil\ARM\ARMCLANG\Bin
- Selected tool variant: mdk_pro
ArmClang.exe: note: - Checkout feature: LIC0=TA...-.....-.....
- Feature version: 5.0201710
- Keil error code: 1

I see a Build Output window similar to this one:


Windows 10 update V1803 causes the following versions of Arm Compiler 6 to fail when used with MDK and a Keil Single-User or Keil Floating license: 6.6, 6.6.1 LTM, 6.6.2 LTM, 6.7, 6.7.1, 6.8, 6.9, and 6.10.


A fix is provided by the Arm Compiler Team since Arm Compiler 6.10.1.


Install a later released version of MDK as these include an ARM Compiler version that fixes this problem.


Compiler version Arm Compiler 6.10.1 must be installed into the ARM sub-folder within the MDK-Installation, i.e.

( managing ARM Compiler versions with µVision is explained here )

If for some reason you can't go for any of these resolutions, contact our Support Team to discuss another solution.


This issue has been fixed in Arm Compiler 6.10.1.

With newer versions than MDK V5.25 this error is not expected to come up.

We apologize for the inconvenience.



The following Discussion Forum threads may provide information related to this topic.

Last Reviewed: Friday, July 13, 2018

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