when i rstart the computer，the ganglia can't work

[notebook0928]

OS:ubuntu16.04
gmetad:heron03.
gmond:heron01,heron02,heron04

I used ganglia to monitor the computer cluster.At first, It worked successfully. However, when i restart the computer, the web of ganglia show nothing.
At first:

After:

the log in /var/log/apache2/error.log shows
[Mon May 06 16:52:14.019273 2019] [mpm_prefork:notice] [pid 15876] AH00169: caught SIGTERM, shutting down
[Mon May 06 16:52:15.071435 2019] [mpm_prefork:notice] [pid 15974] AH00163: Apache/2.4.18 (Ubuntu) configured -- resuming normal operations
[Mon May 06 16:52:15.071468 2019] [core:notice] [pid 15974] AH00094: Command line: '/usr/sbin/apache2'
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/cpu_num.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/load_one.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/cpu_num.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/load_one.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/cpu_num.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/load_one.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/cpu_num.rrd': No such file or directory
ERROR: opening '/var/lib/ganglia/rrds//SummaryInfo/load_one.rrd': No such file or directory

please tell me how to correct it? Thank you all the time