Today I Learned

Missing your POST data in controller ?

So you can see JSON payload in inspector…

{days: [{date: "2018-05-18", unitPricing: {1: 285, 2: 285}},…]}

…but cannot see it in controller?

pry(#<Apis::V1::PricingBulkUpdatesController>)> params
=> <ActionController::Parameters {"controller"=>"apis/v1/pricing_bulk_updates", "action"=>"create"} permitted: false>

Remember to POST it with 'Content-Type': 'application/json' header and sell yourself a nice, juicy facepalm :)