I have tried several times but continue to receive this error: My Trailhead Playground 1 The field 'Offer_Amount__c' either does not exist on the Offer__c object or it is not of type currency.

Please check below points

FL data type should be Currency type 

You are checking challenge in correct playground

https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000A9BQjSAN

Please try in the new playground once.