I have 86 messages in the operator's (0) mailbox and can't seem to be able to access that mailbox. What am I missing?

Dial your voicemail hunt group number and hit * when answered until it asks for your mailbox number, enter 0 and enter passcode to listen to the messages.

Did you see the number of messages in form 50 for mailbox 0? If not check form 19 and see if there is a speedcall in the dial 0 & dial 0 priority form for the tenant. I normally use a separate "General Mailbox" for messages instead of the 0 box and only use the 0 box to transfer to the dial 0 points in form 19.

Yes, in form 50, and that did work, thanks. I'm going to change the routing right away. I usually have the dial 0 go to a front desk phone. If busy, goes to main menu, right?

If a call gets transferred back to the voice mail from an extension that does not have a mailbox, the system will answer with the main greeting.
Make sure your transfer type is unsupervised, so you're sure the voice mail is releasing the call, and allowing the pbx's call forwarding features to do the work.