Our company recently upgraded to Office 365 64 bit version. Before upgrading the 32 bit version of the Anaplan Excel plug in was removed from the computers. After the upgrade, I downloaded the 64 bit Anaplan Excel plug in to install on the user's computers. Each time the install fails, saying "Install ended prematurely, please try again later". The plug in partially installs, the tab is there in Excel, once a user logs in all other buttons are unavailable.
Our add-in versions are all compatible with 64 and 32 bits. Have you got an Anaplan workbook open? If so, the add-in may be disabled because it is either not compatible with the workbook you have (for example 3.4 workbook in a 3.3 add-in) or because you need to convert it (3.4 workbook in 4.0 add-in).
If you don't have a workbook open, then I am not sure.
If the above doesn't help, I would suggest contacting Anaplan Support with information about the workbook you have opened and the add-in version you have now and the add-in version the workbook was last refreshed in.
Magali Pelissier, Product Manager - Extensions (Excel Add-in, PowerPoint Add-in, Google Sheets Add-on) Check out our dedicated Community page in the Platform section!