Check debug logs first. To enable debug logging edit the configuration file grafana.ini:
[log]
# Either "console", "file", "syslog". Default is console and file
# Use space to separate multiple modes, e.g. "console file"
mode = console file
# Either "debug", "info", "warn", "error", "critical", default is "info"
level = debug
Then restart grafana for the setting to go into effect.