As @mokhinurra1 suggests above, check your function for errors. I think the URL_UNREACHABLE error is misleading, when I looked at the execution logs for my function I actually found issues with the code. When I fixed those, the scheduled job ran as e...

I have the same issue... a scheduled job has been running successfully for ages and I made a minor change not affecting the url and now it fails every time with the unreachable url error. A similar function that I havent edited is still working