Alert rule rpc error

I wanted to set an alert to CPU Utilization graph in my dashboard. The datas comes from zabbix server perfectly. When I want to setup the alert rule this error message come up.
"tsdb.HandleRequest() error rpc error: code = Unavailable desc = transport is closing"

I tried to set up another graph with another pc in the same network. But that works perfectly fine, when I tried to set up an alert.
The RPC Services are running in both pc.
Have anyone has a solution for this?

Grafana version: 7.5.7
Zabbix Plugin version: 4.1.5

I updated my grafana to 8.1.5 and the zabbix plugin to 4.2.5. That solved the problem.