Redmine

Hi, I'm new to Redmine, Ruby and Rails and I'm trying to learn as much as possible.
Apparently I have the task configured correctly in a script but it doesn't read the mails(half a year ago when I did a test it worked...), outside the task it returns the following error:

@rake -f /var/www/redmine/Rakefile redmine:email:receive_imap RAILS_ENV="production" host=IMAP-SERVER port=993 username=ADDRESS password=***** unknown_user=accept project=helpdesk unknown_user=accept no_permission_check=1 ssl=true --trace

• Invoke redmine:email:receive_imap (first_time)
• Invoke environment (first_time)
• Execute environment
• Execute redmine:email:receive_imap
  rake aborted!
  OpenSSL::SSL::SSLError: SSL_connect returned=1 errno=0 state=error: certificate verify failed (unable to get local issuer certificate)
  /usr/local/rbenv/versions/2.6.6/lib/ruby/2.6.0/net/protocol.rb:44:in `connect_nonblock'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/2.6.0/net/protocol.rb:44:in `ssl_socket_connect'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/2.6.0/net/imap.rb:1534:in `start_tls_session'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/2.6.0/net/imap.rb:1092:in `initialize'
  /var/www/redmine/lib/redmine/imap.rb:32:in `new'
  /var/www/redmine/lib/redmine/imap.rb:32:in `check'
  /var/www/redmine/lib/tasks/email.rake:121:in `block (4 levels) in <top (required)>'
  /var/www/redmine/app/models/mailer.rb:649:in `with_synched_deliveries'
  /var/www/redmine/lib/tasks/email.rake:120:in `block (3 levels) in <top (required)>'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:281:in `block in execute'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:281:in `each'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:281:in `execute'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:219:in `block in invoke_with_call_chain'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/2.6.0/monitor.rb:235:in `mon_synchronize'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:199:in `invoke_with_call_chain'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/task.rb:188:in `invoke'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:160:in `invoke_task'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:116:in `block (2 levels) in top_level'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:116:in `each'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:116:in `block in top_level'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:125:in `run_with_threads'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:110:in `top_level'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:83:in `block in run'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:186:in `standard_exception_handling'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/lib/rake/application.rb:80:in `run'
  /usr/local/rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rake-13.0.3/exe/rake:27:in `<top (required)>'
  /usr/local/rbenv/versions/2.6.6/bin/rake:25:in `load'
  /usr/local/rbenv/versions/2.6.6/bin/rake:25:in `<main>'
  Tasks: TOP => redmine:email:receive_imap
  @

I am working with the Turnkey template which corresponds to version 4.2.9, I tried to do it with the 5.0.4 template with Debian and without Template and when I executed the second command (bundle exec rake redmine:plugins:migrate RAILS_ENV=production) I got an error (rake aborted too).

https://github.com/jfqd/redmine_helpdesk

Can help me? thank you so much!