LoadComplete displays this message when you are trying to open a project that was created in a LoadUIWeb version earlier than 2.99. LoadComplete does not support the format of such projects. If you open them in LoadComplete, it can fail to load data of some project items. LoadComplete can open and convert LoadUIWeb 2.99 projects only.
To solve the problem, open your project in LoadUIWeb 2.99 first and convert it to the 2.99 format. Then, you can open the project in LoadComplete.
Note that after you convert the project to the format adopted in LoadUIWeb 2.99, you will be unable to open it in earlier versions of LoadUIWeb.