I upgraded my machine to Office 2010 and haven't been able to get this extension to work. Any steps I should take to troubleshoot the problem?

The extension isn't showing up as it used to in 2007. I'm right clicking over an externally sourced pivottable.

 This is one of my favorite tools! Any help would be greatly appreciated.

Maybe try uninstalling OLAP PivotTable Extensions, then download the latest version and be sure to get the 64-bit installer from the Downloads tab. Maybe a fresh install will solve the problem. If not, post back and we'll look into it some more.

I've tried uninstalling and installing OLAP PivotTable Extensions a few times (the 64-bit version). Rebooting my computer a few times also. The program installs without a problem, but I can never access it in excel.

Thanks for trying that simple fix. I've coded all of the registry settings I know of that block it from being loaded into the installer, so it's always worth a shot.

If you click on the PivotTable then press Alt-F11 then Ctrl-G then paste the following into the Immediate window and press enter:

?ActiveCell.PivotTable.PivotCache().OLAP

Does it say True?

If not, then you PivotTable is a native PivotTable that's summarizing some table or other data in the spreadsheet or SQL table. You have to have an OLAP PivotTable (that is, one connected to an Analysis Services server) for my add-in to work.

If the above does say True, the next thing I would recommend is to walk through these installation troubleshooting tips:
http://olappivottableextend.codeplex.com/wikipage?title=Troubleshooting%20Installation

Keep us posted. I'd love to get to the bottom of the issue you're experiencing.