Problem with searching in Jira - 05/10/2018 01:17 EDT

We have a problem with searching in Jira. When we log in, Jira shows messages ,,An unknown error occurred while trying to perform a search" ,, The Lucene health check has failed in your system" and search textbox is frozen. I can't rebuild indexes from settings panel (with Jira locking) - Jira shows message ,,The re-index did not complete successfully. Please refer to JIRA logs for more details."