solr search not working

[instkffff]

Search Plugin installed
Solr connection OK
Solr Indexing Enabled
all checked

but when i search

error: /api/search
SolrError
at IncomingMessage.<anonymous> (/home/NodeBB-1.10.1/node_modules/solr-client/lib/solr.js:991:19)
at emitNone (events.js:111:20)
at IncomingMessage.emit (events.js:208:7)
at endReadableNT (_stream_readable.js:1064:12)
at _combinedTickCallback (internal/process/next_tick.js:139:11)
at process._tickCallback (internal/process/next_tick.js:181:9)

Who can help with it, Thanks.