There could be a variety of things causing this, but given your project, I think the solution posted by paradoc here will likely solve it in your case:
[OpenLevel Travel Failure: Invalid URL - Programming & Scripting - Epic Developer Community Forums][1]
If it does not, please do a search for “Travel Failure; Invalid url” and see if one of the results resolves your issue. If they do not, please start a new AnswerHub post for this specific question as this thread is getting overly long and a little off topic from the original posted question.
-Thanks
OpenLevel Travel Failure: Invalid URL - Programming & Scripting - Epic Developer Community Forums