upgrade f27 to f29 : repositories in archive, how to update

[Adrian Sevcenco]

Hi! I am trying to upgrade my long overdue f27 to f29 (to prepare for 
f30 :)) but i have problems with :
Error: Failed to synchronize cache for repo 'updates'

I already updated my system by pointing the baseurls to the archive
but then if i try
dnf system-upgrade download --refresh --releasever=29 
--setopt='module_platform_id=platform:f29'

i get this 'failed to synchronize' no matter what link i use ...

Is there a way to workaround this?
Thank you!
Adrian