Thank you for reporting this issue!!
We’ve setup a clean Windows 10 environment, downloaded the current .rpt Inspector Online Broker, version 0.6.7 and followed the installation procedure and happy to report that we were able to duplicate the issue you encountered: Download failed: A certificate is required to complete client authentication was shown while it was trying to download additional files, as indicated in the screen shot below and as reported by you:
After additional review and investigation, we have determined that this error happens if you don’t already have installed the required SAP Crystal Reports .NET Runtime version 13.0.23 or higher (as noted here: .rpt Inspector Online - Broker 0.6.7 released) on your system. As part of the .rpt Inspector Online Broker installation, it will automatically attempt to download and install this minimum runtime provided by SAP and it is failing while trying to connect to the SAP site to download the file because it seems that the SAP download location for that file has changed and the SAP site is redirecting to some other location which is throwing this error.
We will release an updated installation that will resolve this problem early next week.