Bug in Plugin Registration Tool for CRM2013 - 6.1

Today I wasted around half-an-hour trying to troubleshoot why Plugin Registration tool was not recognising my custom workflow activity. When I tried to register the assembly, the tool would not display any custom activity.

The version I was using is 6.1.1143.

 

I checked the obvious things

1. Activity class is public
2. Assembly is signed
3. Workflow class extends CodeActivity
4. Built using .net 4.5

Since I could not figure out the reason behind this issue, I tried this in the CRM2015 SDK Plugin Registration tool (v 6.1.0.519).

 

I was able to register the workflow assembly without any issues.  The old plugin registration tool worked without any issues as well. So, currently it seems, it is better to avoid the new plugin registration tool in CRM2013 SDK.