Hello Deepin friends,
I have Deepin on multiple computers and have successfully updated to 15.6 on all but one.
It does not recognise there are updates, so it will not update. Here is some debugging. What should I do?

$ lsb_release -a
No LSB modules are available.
Distributor ID:        Deepin
Description:        Deepin 15.5
Release:        15.5
Codename:        unstable


$ nano /etc/apt/sources.list
deb-src http://sft.if.usp.br/deepin/ panda main contrib non-free

$ sudo apt update && sudo apt full-upgrade
Hit:1 https://deb.opera.com/opera-stable stable InRelease
Hit:2 http://linux.teamviewer.com/deb stable InRelease                                                           
Hit:3 http://linux.teamviewer.com/deb preview InRelease                                          
Hit:4 http://sft.if.usp.br/deepin panda InRelease                                                
Reading package lists... Done
Building dependency tree      
Reading state information... Done
All packages are up to date.
Reading package lists... Done
Building dependency tree      
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.