Some devices have not been polled in the last 5 minutes. You may have performance issues.

Running into this issue:

====================================

Component Version
LibreNMS 1.37-27-ga0c2783
DB Schema 240
PHP 7.0.25-0ubuntu0.16.04.1
MySQL 10.0.34-MariaDB-0ubuntu0.16.04.1
RRDTool 1.5.5
SNMP NET-SNMP 5.7.3

====================================

[OK] Composer Version: 1.6.3
[OK] Dependencies up-to-date.
[OK] Database connection successful
[OK] Database schema correct
[FAIL] The poller (Kellie-PC) has not completed within the last 5 minutes, check the cron job.
[WARN] Some devices have not been polled in the last 5 minutes. You may have performance issues.
[FIX] Check your poll log and see: http://docs.librenms.org/Support/Performance/
Devices:
localhost
192.168.10.1

Did you verify your cron job is working?