This generally means that there isn't enough data for those time frames. I don't know how that is determined but I see this a log. Since it is the overview it probably means that the CM agents or CM services were having issue. Either those or the cluster services were offline, due to a problem or just being off. If you are getting data now I wouldn't worry about it unless it happens again. And just to check, those time frames aren't always missing data right? Try playing around, set it to 1d but then move back in time, do you eventually see data for a day?