Your RVTools version is too old for your current vSphere environment.
This is the most reliable modern fix, as RVTools has moved toward dependency on PowerCLI modules rather than legacy DLLs. rvtools unknown error stsservicedll free
Work through these troubleshooting steps in order. Most administrators find that Step 1 or Step 2 resolves the issue immediately. Step 1: Force Windows and .NET to Use TLS 1.2 Your RVTools version is too old for your
Before moving on to more complex troubleshooting, try these straightforward solutions first. They have a high chance of resolving the problem immediately. Visual C++ runtimes
This solves ~70% of "STSServiceDLL" errors.
This is almost a problem with RVTools itself. It’s an environment issue involving .NET, Visual C++ runtimes, or a mismatch between RVTools and your vCenter version.