The only thing that I can think of is that the image file might possibly be incompatible with v3.1.5
Because looking at the release dates the firmware in the image file is probably v3.0.4 and not v3.1.5.
2023-05-31 v3.0.4 was released
2023-06-16 starfive-jh7110-202306-nvme-minimal-desktop.img.bz2 was released
2023-07-02 v3.1.5 was released
You can probably get it to work if that is the case by modifying some environment variables, but I’m only guessing here, I could be totally wrong.
Still it might be worthwhile flashing with v3.0.4, or possible zapping all your your Das U-Boot environmental variables back to factor defaults (For the new/old Das U-Boot firmware).
Thinking about it a bit more, the second option is the first thing you should try.
env default bootcmd
env default -a
env save
The first two commands will reset everything in RAM, the last command will write them to storage (QSPI NOR FLASH for the VF2), so that they will persist across boots. The above three commands where blatantly plagiarised from here.