Can't write files to SMB shares, followed guides but doesn't not work

So I first followed a guide on here, which laid out how to setup a RAID 1 configuration. I have 2x8tb toshiba drives and wish to maintain a level of redundancy. So if one drive were to fail, I would still have a backup of my data.

After setting up the RAID, I then proceeded to follow the guides on how to setup OMV and SMB shares. Everything went fine, the shares appeared on my network. However when I came to copy files over, I was met by this error.

Now I’ve never used a RAID configuration before, so perhaps this is just a case of me not understanding. But when I went in the “software raid” menu in OMV, I noticed it reported some sort of syncing was taking place, interesting as neither drive had data on them. I did wonder if this might be preventing data from being copied to the shared folders. Frankly I don’t know as I’ve never used OMV before, so i’m hoping someone might be able to help.