Run-time error 91 Object Variable or With block variable not set

Hi all, over the past few weeks we there have been several large Windows 10 updates. Following one such update Hevacomp on each of our Windows 10 machines has stopped working with the above error message. We are able to open the main Hevacomp Design Software panel with the icons but, for example, when we select DDB we get the run-time error dialogue straight away. When we click Netsys, we clock a system type, say heating, then get the project explorer window but it cannot see any of our windows files. Our Windows 7 machines are working fine.

We have uninstalled Hevacomp, and deleted any residual files, although left Crystal Reports. We then restarted the machine, then reinstalled Hevacomp with the latest Update 6 but we still get exactly the same error messages.

The same thing happens on all three of our Windows 10 machines.

Any suggestions?