Thank you for your answer.
I see you are indeed using the 11.2 release build 5822637.
Regarding Fitbit, I can confirm the problem from my end and we already have a fix the will soon be pushed and you'll receive an automatic update.
What concerns me most is the issue with the dialogs. Do you mind running some lines?
First, I would like to see if this happens with other dialogs. Can you please try running:
URLExecute["http://exampledata.wolfram.com/authentication.php"]
That should return something like this:

If you also get $Aborted there, that would be useful evidence to track down this problem. If not, we'll keep investigating.
Now, can you please share the output of:
PacletInformation["OAuth"]
And also of this:
TracePrint[ServiceConnect["Factual"],_OAuthDialogDump`Private`MultipleKeyDialog]