Hi @ Wilders I updated my Aomei Free version yesterday and found out that the Differential Backup option has been removed unless you buy the Pro version. Today I checked on their website and it clearly shows Differential as included. See attached image No warning given about removal. They are entitled to do what they want but not the best way to go about it
As they (still) have the option Differential Backup for the Free (Standard) version in their comparison table, that's not o.k. Perhaps you should report the issue in their Forum (https://www.aomeitech.com/forum/).
I would be more inclined to suspect something has gone awry with the update process rather than the differential option being removed. As you use AOMEI... why not make a full a backup and then try uninstalling and reinstalling the software. Fwiw although I use the Pro version I do not normally update when new versions come along, partly because I've had weird experiences with AOMEI updates in the past. The latest version can wait until I clean install again which to be fair is usually every 12 months or so. I would definitely make a new full backup and then either try reinstalling again (over the top of what you have) or uninstall and reinstall.
I see someone has commented over at AOMEI (perhaps it is even the op's thread there) and that AOMEI say they are looking into it. It would be bizarre to remove differentials from a free product because that is generally the one option that is offered. Incremental backups are usually what you pay for. Over at AOMEI: Removal of Differential Backup From Standard Version — AOMEI Forum (aomeitech.com)