Normally, all files created or refreshed in 3.1/3.2/3.3/3.4 can be converted to 4.0.
Files from 2.6 and 3.0 cannot, because those versions have been deprecated. In this case, the files would need to be first used in any other 3.x version (using the instructions on the deprecation link) before being converted to 4.0.
Can you confirm you are able to refresh the file in 3.1 or 3.2 or 3.3 or 3.4 first, and then try and convert with 4.0?
If that doesn't work, please contact Anaplan Support with the support email functionality under "Help" in 4.0.
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!