Icinga2 dashing dashboard failed to start after complete installation

hey all members hope you are well. i have done complete installation of dashing with proper steps but i am getting errors while starting dashing. please help me to resolve the issue.

OS: ubuntu 20.04

root@icinganew:/usr/share/dashing-icinga2# /usr/local/bin/dashing start -p 8005 --pid tmp/pids/thin.pid
First trying to read environment variables
Environment variables not found, falling back to configuration file config/icinga2.json
Detecting local config file ‘/usr/share/dashing-icinga2/config/icinga2.local.json’.
Using config file ‘/usr/share/dashing-icinga2/config/icinga2.local.json’.
Reading config{“icinga2”=>{“api”=>{“host”=>“localhost”, “port”=>5665, “user”=>“dashing”, “password”=>“icinga2ondashingr0xx”}}, “icingaweb2”=>{“url”=>“http://localhost/icingaweb2”}, “dashboard”=>{“show_only_hard_state_problems”=>false, “timezone”=>“UTC”, “url_prefix”=>“”}}
/root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/urlmap.rb:34:in block in remap': paths need to start with / (ArgumentError) from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/urlmap.rb:25:in each’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/urlmap.rb:25:in map' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/urlmap.rb:25:in remap’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/urlmap.rb:20:in initialize' from config .ru:59:in new’
from config .ru:59:in block in <main>' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/builder.rb:125:in instance_eval’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/rack-2.2.7/lib/rack/builder.rb:125:in initialize' from config. ru:1:in new’
from config. ru:1:in <main>' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/rack/adapter/loader.rb:33:in eval’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/rack/adapter/loader.rb:33:in load' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/thin/controllers/controller.rb:182:in load_rackup_config’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/thin/controllers/controller.rb:72:in start' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/thin/runner.rb:203:in run_command’
from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/lib/thin/runner.rb:159:in run!' from /root/.rbenv/versions/2.6.8/lib/ruby/gems/2.6.0/gems/thin-1.8.2/bin/thin:6:in <top (required)>’
from /root/.rbenv/versions/2.6.8/bin/thin:25:in load' from /root/.rbenv/versions/2.6.8/bin/thin:25:in