Hi Bill.

Sorry, I should have been clearer, I meant to imply -- hold the shift key + mouse-right-click on the Planner installer file (ACPPlanner-x.xx-Setup.msi) then 'Run as Administrator', not the desktop shortcut link to the already installed application, however you have resolved that now.

I spent most of yesterday recording and examining the function logs created when attempting to import a pre-existing plan into the Planner app using Procmon (Process Monitor) from Microsoft Sys Internals on Windows 11, where it crashes the app with the run-time error 438, and on Windows 10 where is doesn't.

Procmon records around a thousand lines of events attributed to Planner alone when attempting to open a pre-existing plan and although I can filter and see many recorded differences in the logs between importing a pre-existing plan into Planner running on Windows 11 and when it is running on Windows 10, I could not find any reference to which object or process is spawning the run-time error 438 and can take this no further myself.

Only Bob has the tools necessary to test the source code for the Planner application against the current Windows 11 24H2 platform and maybe identify which library is either missing or wrongly registered, there's only so much an end user can do with the compiled .exe or .msi files and I don't have the skills needed to dig deeper.

Bob has already stated he isn't releasing any further updates to ACP software in this final year of support so I guess that is the end of Planner as far as full functionality goes for Windows 11 systems, you can create and despatch plans to ACP on Win 11 but not import an existing plan.

If you stick to Windows 10 then you have the ability to import existing plans into Planner and edit and transmit them again to ACP.

I guess the only current workaround for Win 11 is just to open the pre-existing plan in Notepad, read the plain-text plan and then enter the plan contents manually for editing into the Planner U.I. and despatch to ACP.

Unless Bob is prepared to take a look at the Planner source code and compile it to run on Windows 11 24H2 then I think there nothing much else we can do ourselves.

William.