The APIversion on the manifest file is just a number which gets compared with the ingame API returned by function GetAPIVersion().
If the game, upon loading, notices that the API was raised it disables ALL addons in the addon manager.
It will only enable those again, where the API number equals to the one of the current game.
Or if you enable this checkbox "Allow outdated addons" which will just allow the game to enable the addons where this silly number in the manifets txt file is "older"/"lower" than the current GetAPIVersion() func returns.
So basically addons could work fine and all the game does is disable them because this number is lower... This sucks!
And we addon devs always have to get annoyed user requests to "update the addon!!!!" but it's working fine and all you need to do is enable this f***g checkbox in the addon manager or change this API version in the txt file yourself by incrementing it by 1.
It's taking sooo much time to update the files, update the version of the addon as Minion and esoui won't download the addon for you again if you just change the files but not the version (somehow Minion needs to know it got updated so it checks the version).
And then put it into a ZIP archive and upload it, write changelog like "Just raised API" again and again and again.
So what we do is put multiple API numbers after another into the txt file and we are happy the game accepts this and enables the addons automatically if a patch was raising the API.
If the addons do not work afterwards (which we check befor at the PTS in most times and update them where needed, if we find the time) we can even fix them then.
But we do not need to fix working stuff this way.