iTunes Match uploading slowness with eventual error -9810
According to a the Apple Discussion Forum, it's a sign on authentication error (SSL). You should try to sign out, sign on elsewhere and sign back on your iMac. When you do sign out, some flags on the Apple Servers are reset or restored, so you could sign on with the proper speed and permissions again.  

Or you could change from WiFi to Ethernet or vice versa, this is also mentionned as a solution.

The article mentions more solutions, so I suggest you take a look at the article if above information doesn't help you out.