Security levels remind:
Performance - you can perform regular JQL search.
Strict - you can search for secure fields only by using "issue in search" functions.
Disabled - search is not possible.
Important: changing Security level always demands Jira re-index, otherwise changes will not be saved.
Common problems:
Troubleshooting checklist:
1. make sure the search is performed by the user who is authorized to view the secure field
2. make sure there are no typos in the search query
3. use searching query according to Secure level searching mode settings:
for JQL search - Search level has to be set to Performance
JQL search won’t work for fields in Strict mode, you will have to use "issue in search" function or switch to Performance mode
4. check if there is no warning for the particular field on Search security level page, if warning sign occurs - save configuration once again and perform re-index.