Sometimes one of your widgets might fail to load, with the error "Too many rows, try using a shorter date range or fewer dimensions". This is an error message returned by Funnel, which indicates that the query would result in too many rows and was therefore aborted. We do this for performance reasons, and to avoid sending huge or incomplete responses.
There are a few different things you can do to handle this situation, but more or less it all boils down to reducing the cardinality of the data returned. The simplest way to do this is to reduce the segmentation in your query, i.e. by removing a dimension or a filter. Time series widgets will always include the Date dimension, which means that if a time series widget fails to load you can either reduce the time span or use another type of widget that displays the totals for the request period.