There is a limit on the timeseries api. It will return max 2000 values.
Depending on the frequency of your data ingest this could be the reason why you only see 15 min.
If you want to visualize the 48h you could also use the aggregates api.
See also
https://gettingstarted.mendixcloud.com/link/path/93/Build-a-MindSphere-App---Continued
there the timeseries and aggregates api is used.
Or just use the aggregate Chart from the WebComponent from here:
https://appstore.home.mendix.com/link/app/110119/
It does all the heavy lifting...
I suspect the input parameter values aren't making it correctly to the URL parameters in the REST call. What's happening in DS_TimeSeriesDateFromToParameter? It may be helpful to log exactly what URL (and params) are being sent to MindSphere.
Let me add it here aswell
'from='+formatDateTime(parseDateTime(formatDateTimeUTC($TimeSeriesFilter/From, 'MM/dd/yyyy''T''HH:mm:ss.SSS'), 'MM/dd/yyyy''T''HH:mm:ss.SSS'), 'yyyy-MM-dd''T''HH:mm:ss.SSS''Z''')
+
'&to='+formatDateTime(parseDateTime(formatDateTimeUTC($TimeSeriesFilter/To, 'MM/dd/yyyy''T''HH:mm:ss.SSS'), 'MM/dd/yyyy''T''HH:mm:ss.SSS'), 'yyyy-MM-dd''T''HH:mm:ss.SSS''Z''')