Thank you so much for your help. I ran the following command to disable the threshold:
PUT /_cluster/settings
{
"persistent" : {
"cluster.routing.allocation.disk.threshold_enabled" : false
}
}
After that I restarted the elasticsearch and Kibana services, ran the following command:
PUT .kibana/_settings
{
"index": {
"blocks": {
"read_only_allow_delete": false
}
}
}
Now it works again.