No graph in cpu utilization

[sh2p]

Hi all,
I'm currently trying to check the cpu utilization and io wait of a linux server on zabbix graphs and figuring out the issues. My problem is when I want to check a limited time period on the graphs there is no data shown on the graph but when I scale out the graph a little bit it does shows a graph but I thinks it's because that in that scale the data could be shown. The photos of the graphs are attached. Is there any way to check the log files, if yes, where are the log files? Why there is no data captured in these periods of times by zabbix?
Thanks in advanced.

[sh2p]

Maybe item interval is bigger than yours 3 min period on graph. So graph don't have two points to connect.

Hello and thanks for your fast reply,
I've checked the item time interval of the host and it's set to 30s which is lower than the time period I wanted to check.