No auto update (Linux Debian)

[MarmiteSandwich]

I am running Minimserver on a Linux PC and installed 0.8.4 originally. Recently I have had the message to update to 0.8.5 because 0.8.4 is no longer supported. I manage the installation via Minimwatch on a W10 PC, which says that auto update on Minimserver is set to true, but it hasn't happened and there is no option in the packages tab to install a new version.

Any ideas why it hasn't happened, and what Linux command I need to issue to get it to behave? I am not a qualified Linux user, but can use Putty to access the device.
Many thanks.

Turnkey Linux is Debian Linux 8 and runs on an Asus eee box PC with 2GB of RAM.