VBE6ext.olb is a component of Visual Basic for Applications (VBA). VBA is installed with OS Update, but it might be present from other sources, most noticeably from Microsoft Office product family -- many products, whether part of Office Suite, like Excel, or not, like Project, include VBA. So, the first thing I would try is to uninstall the Agent, then uninstall OS Update, then install OS Update (make sure it belongs to the same version as the Agent you are going to install), and then install the Agent again. When you do it, make sure that other applications, especially known to include VBA, are not running when you do these uninstallation/installation steps.
If this does not help, I'd put attention to presence of VBA installation from a source different than Enterprise Synthetic Monitoring. You can check the presence and the version of C:\Program Files (x86)\Common Files\Microsoft Shared\VBA\VBA7.1\VBE7.DLL and check VBA Usage and Available Patches to see if this version is supported.
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Thanks Yuriy for the update.
I tried uninstall and re install.. and while Installing ES agent I have chosen different drive to install instead of C drive
Now I am not getting vbe6ext.olb could not be loaded message
However this is the new error
Can you please suggust me how to proceed further