It's not possible to search anything on Graylog search. Relevant errors seem to be:
a few seconds ago graylog_231 8691ce60-de29-11eb-8767-0200001a24a4 ElasticsearchException[Elasticsearch exception [type=cluster_block_exception, reason=index [graylog_231] blocked by: [TOO_MANY_REQUESTS/12/disk usage exceeded flood-stage watermark, index has read-only-allow-delete block];]]
Elasticsearch nodes disk usage above flood stage watermark (triggered 4 days ago) Elasticsearch nodes disk usage above high watermark