Update nextcloudVM from ver 13 to 15

I downloaded and ran the nextcloud VM from tech n me awhile ago. Using there update script I came across a problem where I can’t updated from 13 to 15.

When i log into my nextcloud server admin interface and try and use the built in app for updating to 14, I get a permission’s error. When I ask over at the VM github section, I’m told to ask here. Is there anyone else who had this problem? and can point me in the right direction?

Edit: I’m using ubuntu server 16.04.3 LTS, and nextcloud version 13

Please read the docs: https://docs.hanssonit.se/s/W6fMouPiqQz3_Mog/virtual-machines-vm/d/W7Du9uPiqQz3_Mr1/nextcloud-vm-machine-configuration