I too am experiencing this “Press the log in button and poof” issue.
I’m on a Ps5, made sure it (PS5)was updated, all and any psn Updates in general were updated. Verified other games online/ offline worked. Reck all cables/ internet/hdmi/ ect. All were as they should be. Verified internet connection, all other games using either online play or offline play. Confirmed 878 download/ 40 upload both via my PlayStation and via laptop (slightly faster).
Restarted, cleared any unnecessary games and their data off my ps5 just as a precaution. Confirmed on PlayStation store the purchase/ and download of Dawntrail. Not sure what else to do? Initiated a “ticket” to SE and awaiting their response (sent this am).
It’s just weird because like others have said it goes good until you press the log in button…