Hello,
I'm new to xcp-ng but it seems I have the same issue.
I have done some tests to resolve this (but failed) and if I remember, when i look at /var/log/audit.log in the first host of my cluster, I saw this error :

... [ failure: repodata/repomd.xml from xcp-ng-linstor: [Errno 256] No more mirrors to try. https://repo.vates.tech/xcp-ng/8/8.3/linstor/x86_64/repodata/repomd.xml: [Errno -1] repomd.xml signature could not be verified for xcp-ng-linstor ...

but installing manually xcp-ng-linstor with yum does not solve the issue.

PS : In your case, it seems you want more than 7 disks in your xostor and I think you need between 3 and 7 disks.