Replaced hard drive and cannot restore. Was in the Insider program.

I have an Xbox One S digital that suffered an HDD failure so I replaced it with another and downloaded the OSU from Microsoft's website ad followed all instructions to set up the new drive but I cannot get the OSU to restore and am getting error "E101 00000504 8B50041" which from my research I have concluded that this is due to attempting to restore an older OS than what was installed before. I was in the Xbox delta insider preview and I cannot find any way to get Insider OSUs from anywhere. Is my only choice to wait until the beta becomes publically released and then restore or are there other options? I did "downgrade" from the stock 1TB HDD to a 500GB HDD I had but I haven't read that downgrading storage can cause any issues. If there is anything else I need to add let me know, please. Thank you in advanced.