Upgrading from versions older than 0.9.255
New versions greatly optimize DOTweenAnimations startup, but require all animations to be reassigned. It's very simple, don't panic. Just select each gameObject that has a DOTweenAnimation attached (one by one, not all together) then save your scene: that is enough to update it automatically.
In case you should forget, a warning will appear while playing, telling you exactly what to do and which gameObject to select.
Upgrading from versions older than 0.9.100
When you upgrade to DOTween Pro 0.9.100 or later versions, you will get some "Missing Component" warnings in Unity's console. Drag & drop the DOTweenAnimation Component (from the Demigiant > DOTweenPro project folder) to the Script field of each of those Components, and you'll get all your animations back, with the settings you previously stored.