Before trying the following please read the whole post as the answer might be a misunderstanding...
Use the SketchUcation ExtensionStore to install JointPushPull, FredoCorner and LibFredo6 again.
Then restart SketchUp to sync everything.
If you are still getting the licensing error[s] check that you have installed the proper license for the extensions
I suspect that you have a license for Fredo's RoundCorner and this is not the same as the installed FredoCorner, which expects a separate license file.
There have been a few reports of users confusing the two extensions and their respective licenses.
Although the two are similar in what they do, they are not identical, and they need to be licensed separately.
So ensure you have the correct extensions installed and their matching licenses validated,
after that a SketchUp restart should get both properly licensed and error free.