Cannot check in online

I tried to check in online in order to receive electronic boarding pass, but was forced to download this app in order to scan my passport to complete the process. After first attempt the app tells me it was unable to complete the check in process at the final step. So I spent another 15 minutes starting from scratch and encountered the same problem...the worst part is that it doesnt save anything at any step. Definitely a bad experience

j-ace1990 about United Airlines, v2.1.10