I've had this setup for several months now with no issues. However, it appears Mailchimp changed their API keys to use a new datacenter (new API keys end in -us2 instead of -us1).
Anyway, with this new API key, I get the following error inside Analytics360:
Error: Invalid Mailchimp API Key: <<MY API KEY >> You are accessing the wrong datacenter. Your client library may not properly support our datacenter mapping scheme.
If I disable the WPMU Dev Mailchimp plugin, Analytics360 works fine and brings in the list of subscribers properly. If I re-enable the Mailchimp Newsletter Integration plugin, the error returns. Any ideas?