Odroid c2 sd card error

Hi there!

I have an Odroid C2 SBC running a Seafile server - or rather, it was running until a few days ago. After a DietPi update, unfortunately, it no longer starts. I connected a display to it, and was greeted by the following error message:
mmc0: error -110 whilst initializing SD card.

Great. So I bought a new SD card, flashed the latest downloadable image onto it, booted it up - and was met with the same message. So I assume the SD cards themselves are not the issue.

I also tried disabling updates in dietpi.txt, but that didn’t change anything.
Any idea what could be done?

Thank you in advance - and congratulations on the excellent work you’re doing!

Can you please fill out the troubleshoot template. We need to know which kernel you use and some other stuff.