Yep. "Technical issues" on my end, too. For reference: Android, everything updated. 100% DL operated flights.

Checking in today for an international flight (with applied GUC) tomorrow, and got "technical issues". At first, I was worried that I was dealing with a ticket that wasn't correctly reissued. Thankfully, that's not the case. A couple refreshes let me complete the check-in process, and the app check-in even let me scan my passport so that it properly shows as "verified" (this is a first for me, so: maybe DL is finally getting something right in the app?). The check-in process choked when trying to add a checked bag. I removed the checked bag and was able to complete the process. Once the check-in was complete, I again got "Technical issues". I can see view my boarding passes, though - and have added them to my digital wallet as a backup.