The LoopSign Calendar Widget needs a service account that has rights to read the resource calendars (Meeting room calendars). Due to Microsoft throttling policy one account should only be used on up to 15 different screens. So please create one service account pr. 15 screens that are to show the room schedules. More information on the Client throttling policy can be found here – EWS Throttling
This default values can be changed, or simply just make several service accounts. More
information on the Client throttling policy (EWSMaxConcurrency attribute). can be found
here. https://technet.microsoft.com/en-us/library/dd297964(v=exchg.141).aspx
LoopSign needs all of the rooms that are to be shown to be present in one or several room lists.
By default rooms are not organized in any lists, so if your exchange is not configured with room lists, please do so.