Thank you so much for your direction. Rails console is showing nothing wrong...

Started POST "/rails/active_storage/direct_uploads" for 127.0.0.1 at 2020-11-30 23:45:46 +0700

Processing by ActiveStorage::DirectUploadsController#create as JSON

  Parameters: {"blob"=>{"filename"=>"IMG_6766.JPG", "content_type"=>"image/jpeg", "byte_size"=>3809114, "checksum"=>"XXXXXXXXXXXXXXX"}, "direct_upload"=>{"blob"=>{"filename"=>"IMG_6766.JPG", "content_type"=>"image/jpeg", "byte_size"=>3809114, "checksum"=>"kJgGR4MU3XfpbzvoEZD83A=="}}}

   (18.0ms)  BEGIN

  ActiveStorage::Blob Create (21.2ms)  INSERT INTO "active_storage_blobs" ("key", "filename", "content_type", "byte_size", "checksum", "created_at") VALUES ($1, $2, $3, $4, $5, $6) RETURNING "id"  [["key", "XXXXXXXXXXXX"], ["filename", "IMG_6766.JPG"], ["content_type", "image/jpeg"], ["byte_size", 3809114], ["checksum", "kJgGR4MU3XfpbzvoEZD83A=="], ["created_at", "2020-11-30 16:45:46.410051"]]

   (2.9ms)  COMMIT

  S3 Storage (5.8ms) Generated URL for file at key: XXXXXXXXXX (https://XXXXXXXX.sfo2.digitaloceanspaces.com/x5e5iv60zg38xhzzbhitpxywvsfn?X-Amz-Algorithm=AWS4-HMAC-XXXXX&X-Amz-Credential=XXXXXXXXXXXXXX%2F20201130%2Fsfo2%2Fs3%2Faws4_request&X-Amz-Date=20201130T164546Z&X-Amz-Expires=300&X-Amz-SignedHeaders=content-length%3Bcontent-md5%3Bcontent-type%3Bhost&X-Amz-Signature=XXXXXXXXXXXXXXXXXXXX)

Completed 200 OK in 70ms (Views: 1.1ms | ActiveRecord: 42.1ms | Allocations: 5741)