Hi Derek,
Can you tell me please if the your staff email configuration is on Exchange or in POP/IMAP.
Please note that full calendar synchronization and free/busy (availability) sharing is only supported when using Microsoft Exchange (or Microsoft 365 / Outlook.com accounts, which run on Exchange Online).
POP and IMAP email accounts do not support calendar syncing, shared availability, or resource booking features , since they can only handle email, not calendar or contacts.