NextCloudPlus not yet initialized, trying again in a few seconds …

My setup: NCP on raspberrypi with system and data on 128 GB SD card.

I installed NCP two days before and did a backup yesterday. After the backup, I was asked to create a new database, so I think I did the backup to the sd-card where my data was stored.

I wanted to reinstall NCP, the setup screen with the passwords appears, but clicking on “activate” leads to:
“NextCloudPlus not yet initialized, trying again in a few seconds …”
Refreshing the page generates new passwords, but not to a successfull installation. I copied the image again with etcher to the same and another SD-card, but the error message remains.

You already found this similar topic:

Try a different power supply. I already had so many problem due to that and the effects are really strange.