I really don't think this is a sitemap issue. I don't know the language well enough to speak of this but the error I am getting is

[ERROR] [o.u.i.items.ItemUIRegistryImpl:411 ] - Cannot retrieve item 'itm_office_mqtt_motion_switch' for widget org.openhab.model.sitemap.Switch

This makes me think it is an item issue not a sitemap issue. I captured this startup information from the log file:

[DEBUG] [.b.mqtt.internal.MqttActivator:34 ] - MQTT binding has been started.
[DEBUG] [i.internal.GenericItemProvider:334 ] - Start processing binding configuration of Item 'itm_office_mqtt_string (Type=NumberItem, State=Uninitialized)' with 'MqttGenericBindingProvider' reader.
[DEBUG] [b.mqtt.internal.MqttItemConfig:71 ] - Loaded MQTT config for item 'itm_office_mqtt_string' : 1 subscribers, 0 publishers
[DEBUG] [o.i.t.m.i.MqttBrokerConnection:476 ] - Starting message consumer for broker 'officepi' on topic 'office_string'
[DEBUG] [m.internal.MqttEventBusBinding:61 ] - MQTT: Activating event bus binding.

It shows the process for binding the itm_office_mqtt_string Item, but there is no mention of the binding of the itm_office_mqtt_motion_switch Item. Should there be? If so, anyone know why it might not be there?

As I said above, when I comment out the itm_office_mqtt_string Item in the items file, OpenHab refreshes (see below) and allows the itm_office_mqtt_motion_switch Switch Item to function.

[INFO ] [c.internal.ModelRepositoryImpl:97 ] - Refreshing model 'mini.items'
[DEBUG] [i.internal.GenericItemProvider:154 ] - Processing binding configs for items from model 'mini.items'
[DEBUG] [m.i.MqttGenericBindingProvider:73 ] - Removing message consumers for item itm_office_mqtt_string
[DEBUG] [o.i.t.m.i.MqttBrokerConnection:505 ] - Unsubscribing message consumer for topic 'office_string' from broker 'officepi'
[DEBUG] [m.i.MqttGenericBindingProvider:106 ] - Removing message publishers for item itm_office_mqtt_string
[DEBUG] [b.mqtt.internal.MqttItemConfig:71 ] - Loaded MQTT config for item 'itm_office_mqtt_motion_switch' : 1 subscribers, 0 publishers
[DEBUG] [o.i.t.m.i.MqttBrokerConnection:476 ] - Starting message consumer for broker 'officepi' on topic 'office_motion'
[DEBUG] [i.internal.GenericItemProvider:133 ] - Read items from model 'mini.items'

The sitemap works when the item can be retrieved, but I don't know why only one item is being retrieved, not both.

Thank you for looking at this. Right now the items file shows as

/* Office Items*/
Switch itm_reset_office_count "Reset Library Count" (gr_office)
Number itm_office_hit "Office PIR Hits [%d PIR Hits]" (gr_office)
DateTime itm_office_hit_tstamp "Last Updated [%1$tA, %1$tI:%1$tM %1$Tp]" (gr_office)
Number itm_office_mqtt_string {mqtt="<[officepi:office_string:state:default]"} (gr_office)
Switch itm_office_mqtt_motion_switch {mqtt="<[officepi:office_motion:command:default]"} (gr_office)

The sitemap file has:

Group label="Office" item=gr_office
{
Text item=itm_office_hit
Text item=itm_office_hit_tstamp
Switch item=itm_reset_office_count
Switch item=itm_office_mqtt_string label="What my Raspberry Pi said:" mappings=[1=Yes, 2=No, 3=Maybe]
Switch item=itm_office_mqtt_motion_switch label="motion switch"
} //END OFFICE FRAME

With this setup, I can publish mqtt messages with mosquito on my Raspberry Pi to
highlight the itm_office_mqtt_string Switch in OpenHab Display: Yes, No or Maybe. But the I
cannot publish mqtt messages to the itm_office_mqtt_motion_switch, OpenHab does
not get them. Moreover, when I toggle the switch on the OpenHab Display, I get:

[WARN ] [.w.internal.servlet.CmdServlet:100 ] - Received command 'TOGGLE' for item 'itm_office_mqtt_motion_switch', but the item does not exist in the registry

[ERROR] [o.u.i.items.ItemUIRegistryImpl:411 ] - Cannot retrieve item 'itm_office_mqtt_motion_switch' for widget org.openhab.model.sitemap.Switch

If I comment out the itm_office_mqtt_string Switch Item, then I can publish mqtt
messages with mosquito to toggle the itm_office_mqtt_motion_switch Item on
OpenHab Display to ON or OFF. I can also toggle the switch on the OpenHab Display without
error.

Also when I comment out the itm_office_mqtt_string, and close the item file this occurs:

Refreshing model 'mini.items'
[DEBUG] [i.internal.GenericItemProvider:154 ] - Processing binding configs for items from model 'mini.items'
[DEBUG] [m.i.MqttGenericBindingProvider:73 ] - Removing message consumers for item itm_office_mqtt_string
[DEBUG] [o.i.t.m.i.MqttBrokerConnection:505 ] - Unsubscribing message consumer for topic 'office_string' from broker 'officepi'
[DEBUG] [m.i.MqttGenericBindingProvider:106 ] - Removing message publishers for item itm_office_mqtt_string
[DEBUG] [b.mqtt.internal.MqttItemConfig:71 ] - Loaded MQTT config for item 'itm_office_mqtt_motion_switch' : 1 subscribers, 0 publishers
[DEBUG] [o.i.t.m.i.MqttBrokerConnection:476 ] - Starting message consumer for broker 'officepi' on topic 'office_motion'
[DEBUG] [i.internal.GenericItemProvider:133 ] - Read items from model 'mini.items'

Both work individually, but the OpenHab doesn't bind both topic at the same time. Somehow when the first mqtt item is picked up the second one isn't, but if I comment out the first one, then the second one is picked up.

I don't understand what I should do to make both work. Any suggestions appriciated.

I have OpenHab up and running. I have mosquito up and running. I have a switch item with a mqtt binding that works. When I try to add another switch item with a different mqtt topic, the mqtt binding process never picks it up. But if i comment out the first switch item, then the second switch will get picked up with mqtt binding. Each one will work indiviudally, but I can't get both to work simulanieously. Any advice would be appreciated.