Now I think I see the issue...
You are perhaps a new [or renamed] user of the SketchUcation toolset on that computer ?
Each SketchUcation toolset user is 'registered' on each computer that they use it on.
So because you have not yet registered, there is an ExtensionStore dialog which opens at start up, and you simply need to log-in to SketchUcation using that.
Enter your SketchUcation member-name and current SketchUcation password in the two fields nad submit them.
You'll need at internet connection at that time...
Once your details are received and verified by the SketchUcation server [it takes only a second] an encrypted version of your data is saved in your user's AppData subfolder [rather like a 'cookie'], and thereafter you should not see that SketchUcation log-in dialog again at start up, unless of course you have deliberately logged-out of the main ExtensionStore dialog [bottom-right (|) button], in which case you will be prompted to log-in again...
If you have any issues with this come back again...
PS: Although the Plugins and Extensions Managers can be used to disable other scripts, the ExtensionStore cannot disable itself !
So it will load at start up.
You could however disable its Extension using the native Preferences > Extensions dialog, but then you'll lose all of its tools...
If you are going to do that you might want to enable all Plugins in its Manager - otherwise these will not be visible to SketchUp at all...
PPS: Please ensure that you also have the latest version of Internet Explorer installed [v11?] - SketchUp needs it - and that your Internet Options [Control Panel] is not set to be too strict etc
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