Start os on pi 4 is asking for username and password

I flashed start OS on my Pi 4 and one of the daemons, “startmontools.service” failed
and brought me to a login page on the terminal

Have you been following our specific Flashing Guide for Raspberry Pi? If followed step by step there should be no issues.
Please attempt the flashing once again making 100% sure to follow the instructions and using the correct startos-…_raspberrypi.img.gz file.
Once that is all done, you should be able to keep going with the Initial Setup Guide.