For future reference, everything you did was wrong. And you are using the term "mount" incorrectly. "Mount" is when the OS loads the filesystem of a disk to make its files accessible.

Please ask for help if you are not sure what to do.

1 hour ago, JorgeB said:

The partition is not using the whole disk, v7 didn't care about that, but v7.1 will use the actual partition with the array stopped type:

sgdisk -o -a 8 -n 1:32K:0 /dev/sdX

Replace X with the correct disk1 identifier, then reboot. Disk1 will show as wrong again, do another new config and start the array, post new diags if it still doesn't mount.

Thank you very much, this has fixed the issue for me! The array now starts properly, the files are all still there on disk1.