Getting server error 500 on calling a method ruby

Hi when i call a function i get the following error log. Please help decipher it.

NoMethodError (undefined method `first' for #<Matching:0x0000000875a050>):
  app/mailers/matching_mailer.rb:6:in `new_matchings_for_customer'
  app/models/matching.rb:133:in `block in create_matchings_from_service'
  app/models/matching.rb:126:in `each'
  app/models/matching.rb:126:in `create_matchings_from_service'
  app/models/matching.rb:30:in `process_matchings_for_service'
  app/models/payments/subscription.rb:94:in `find_matchings'
  app/models/payments/subscription.rb:85:in `after_create_actions'
  app/controllers/contractors/subscriptions_controller.rb:51:in `subscribe'
  app/controllers/contractors/subscriptions_controller.rb:19:in `create'

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