If you sync in Puppet Forge into Satellite 6.1, you may think that it's not working properly. Looking at the task progress, it states 0%. Looking in Sync Status, it says something like:
'Total module count: 3970.'
..but no progress indicated.
This is a bug, there are actually plenty of stuff happening. You can track the status by doing a grep in /var/log/messages on your satellite server.
# watch 'echo "Puppet modules synced in so far: $(grep "pulp: requests.packages.urllib3.connectionpool:INFO: Starting new HTTP connection (1): forge.puppetlabs.com" /var/log/messages|wc -l)"'
Puppet modules synced in so far: 1247
Sync time, on my VM with 8GB RAM and limited CPU was ~1-1,5 modules / second. So, approx. 1 hour to sync in all modules in Puppet Forge.