Accepting or declining meeting invitations is a function of the calendar system itself, not the Zoom Room.
For example, with O365 or Exchange, the settings of the resource mailbox control what invites are accepted (or not). So, you may need to follow up with your calendar system provider (e.g. Microsoft for Exchange or O365, or Google for Google Calendar).
One thing that I have seen as an issue in the past with O365 and/or Exchange: if a meeting invite originates from an external third party, and a user forwards it to a calendar resource associated to a Zoom Room, an O365 and/or Exchange admin must execute the powershell command Set-CalendarProcessing with appropriate switches to enable the room resource to process the external meeting invite (the invite is considered "external" even if an internal users forwarded it). Follow example 8 in Microsoft's documentation, but set the flag $true instead of $false:
Set-CalendarProcessing -Identity "Room 221" -ProcessExternalMeetingMessages $true