"extension already exists" error when uploading new version of addon

Hi,

I have an addon which the version number is 910.14.0.3.

If I build a new version (e.g. 910.14.0.4) and attempt to upload it in Extension Manager it complains that "extension already exists".

I can remove the addon and add the new version, but this is painful as it loses all the company and user assignments.

The new version number is higher than the old, what am I doing wrong?

How do you upgrade the addon?